1. New Super Mario Bros.
2. Picross 3D
3. Mario vs Donkey Kong (2: March of the Minis)
4. Professor Layton (and the Diabolical Box)
5. Zelda: Phantom Hourglass
6. Tetris DS
7. Meteos
8. Zoo Keeper
9. Yoshi's Island DS
10. Okamiden

In no particular order:
Mega Man Zero Collection, Jump Ultimate Stars, Kirby Super Star Ultra, Kirby Mass Attack, Retro Game Challenge, Rhythm Heaven, WarioWare DIY (shame I sold it awhile back, it introduced me to spriting and inspired me to get into Game Design XD ), Mario & Luigi: Partners in Time, Yoshi's Island DS (Although I still consider its bonus stages and anything post-world 3 to be "D**k Move: THE GAME" ), and Puyo Pop Fever (my very first DS game).

1) The World Ends With You - one of my personal favorites.
2) 999 - Really freaky game. It will hook you and prevent you from sleeping for days. I can't remember a time I beat a 20+ hour game as quickly as I did
3) Pokemon Black/White - 'Nuff said
4) Super Robot Taisen OG Saga: The Endless Frontier - Giant robots, Giant boobs, and Giant jokes about giant boobs and giant robots. Such an awesome game.
5) Radiant Historia - Really cool spin on time travel. Great story too.
6) Castevania: Order of Ecclesia - One of the best platformers on the DS
7) Henry Hatsworth and the Puzzling Adventure - A great and unique combination of the platfomer and puzzle genres. Funny too.
8) Might and Magic: Clash of Heroes - If you have a 360/PS3, get it on that. It's cheaper and pretty. But this one is portable. Both are really fun.
9) Either of the Zelda DS games
10) Big Bang Mini - really cool shooter, that's easy to pick up and play for a few minutes. You can probably find it on the cheap too.

1.Pokemon Black/White
2.Pokemon Soul Silver
3.Pokemon Diamond/Platinum
4.Phoenix Wright
5. Scribblenauts
6.Megaman Starforce 1,2,3
7.Kingdom Hearts 358/2 Days
8.Pokemon Ranger
9.Pokemon Mystery Dungeon
10. Mario and Luigi RPG 3
Actually I have more but let's just say Kirby and Starfy are 11 and 12. I have more DS games to buy so I'll get them sooner or later I guess.

In no order, really:
1. Ace Attorney games (including Miles Edgeworth ones, not that I could play the second one because it isn't in English. TT_TT)
2. Animal Crossing: Wild World.
3. The Legendary Starfy.
4. Ghost Trick: Phantom Detective.
5. Mario and Luigi: Partners in Time.
6. Mario and Luigi: Bowser's Inside Story.
7. Kirby Squeak Squad.
8. Kirby Super Star Ultra.
9. Any Professor Layton game.
10. Spongebob Squarepants: The Yellow Avenger. (I bet not many people knew about the existence of this game, but I had fun with it for a while... Although, I guess now, it kinda sucks....)

Honorable mentions:
Any Mario game, WarioWare: Touched!, WarioWare: DIY, Solatorobo, Electroplankton, Chibi-Robo: Park Patrol, Cooking Mama, Cooking Mama 2: Dinner With Friends, Cooking Mama 3: Shop and Chop, any Pokemon game. I'll post more if I think of any.

my favorites are:
game and watch collection(from club nintendo)
zelda four swords anniversary edition(DSiware)
pokemon white
new super mario bros.
mario kart DS
super mario 64 DS
game and watch gallery(3DS virtual console)
game and watch DSi ware games(DSiware) (esppeccilay ball vermin and DK jr.)
super mario land 2: 6 golden coins(3DS virtual console)
AR games (3DS built in software)
i will add game and watch collection 2 and super mario 3D land and mario kart 3DS when i get them

Eliminating ports/remakes of games that had already been released in the West (sorry Chrono Trigger & Super Mario 64 DS) and limiting things to one title per series (and in no particular order):

999: Nine Hours, Nine Persons, Nine Doors
Kirby Canvas Curse
Mario & Luigi: Bowser's Inside Story
Mario Kart DS
Picross DS
Phoenix Wright: Ace Attorney - Trials and Tribulations
Castlevania: Dawn of Sorrow
Hotel Dusk: Room 215
Radiant Historia
Retro Game Challenge

This is not in any particular order, just as they came to my head:

1. Dragon Quest IX :Sentinels of the Starry Sky - This one has to be the best if not one of the best ds games out there, all the character customization, the co-op multiplayer, it has a well crafted story line, great battle system, it can even be played for ever with all the quests, random extra dungeons, alchemy and extra quests and it starts off guiding you through the story giving you more and more freedom as you go but leaving questions unanswered till you start the right quests after you clear the main story, also legacy bosses that you can level up bring on a greater challenge. Better yet I never played any of the others and was able to play and not be lost, plus I've easily burned more then the 360 hours the game's current file thinks I've played, not including the 45 hours, 5 mintues short of 46 in multiplayer on my current file.

2. Pokemon SoulSilver Version - HeartGold is pretty much the same thing but I got to go with my favourite version and I don't have Heartgold. It takes the largest and likely best of all pokemon games and expands it with new areas and things to do. It also has the useful pokewalker to get pokemon, level them up and collect items as you walk and if you go for a walk without a pokemon, you might just get a free one.

3. Golden Sun Dark Dawn - I never played the others and this made me upset with that because I use to see them in stores but I never asked for a copy, it is fantastic. The art style is beautiful, combat is easy to pick up and the game has managed to get me to play it through 6 times and I'm still working on my most recent play through, it's has an engaging story that leaves you waiting the final game and makes me wish I could have seen the first one. You can miss things going through causing many play throughs that can take about 40 hours each, the game is loaded with secrets and if it's to easy for you to clear, go do the optional bosses, they will destroy you, I would say how but it would ruin the surprises.

4.The Legend of Zelda: Spirit Tracks - If you like trains get this, don't think about it, Nintendo has the train travel to perfection. It has a pile of side quests and some tricky dungeon puzzles. Combat isn't that difficult in this one but it can be tricky. The world is one of the most expansive and you get to slowly increase it's size making it huge and it can take a long time to travel the world because of the massive space if you don't use the short cuts. The only downside is there are not a lot of repeatable side quests, but the train customization and whip are a real treat. I've actual enjoyed just travelling by train for no reason, just enjoying the scenery and music, the train travel is that good and the game still feels like a Zelda game. Also the multiplayer for up to four people can be lots of fun.

5. Metroid Prime Hunters - This one is a gem, it has great multiplayer with a vast map variety, and power ups, it has a still going strong online mode but sadly cheaters too. The story mode while not the best does help you adjust to your controls of choice and let's you explore the areas that will become multiplayer battle grounds. Also you can set up matches just to play cpus if you have no friends or online and each character is unique so there is even an element of strategy involved here.

6. Super Scribblenauts - This is a perfected puzzle game, you can have what ever you want to solve the puzzles, so it comes down to your creative thinking, and makes for a fun time and this version has better controls and adjectives to make the game easier to play and control, but still sometimes can be very challenging. Also it has a tenacity to be over whelmed and freeze if you put to much stuff on screen.

7. Kingdom Hearts 385/2 days - this one is both excellent and a heartless. It has a great combat system explains what happened before kingdom heart 2, which I am yet to play. It has a nice difficultly curve, with only a few missions you might want to skip and come back to and best of all, it has a completive co-op multiplayer, where everyone gets to use there own unique characters and fight through most missions. However some levels are borrowing and the reputation can wear on the experience but is still a blast, just beware of the Dustflier.

8. Pokemon Black Version - When I played pearl, this is what I expected, rotating parts of the world and different views of many various areas. It even brings you back to red and blue where every pokemon is new and fresh, the thing I expected out of ruby and sapphire and this one does not drag on like pearl version. It also has a real story, that's original and gets you interested in the characters and plot. Also the champion is keep as an after game battle and it is really good because the game gives you stronger areas to level up to get ready for that battle, making this one of the best pokemon games yet. Plus the shiny encounter rate is up.

9. The Legend of Zelda: Phantom Hourglass - The sea exploration is not near as good as the rail travel in Spirit Tracks but this is still Zelda and it has some good qualities. Like it has some really good boss battles and the repeat dungeon is not bad. It has a weak online but nice 2 player mode. The fairy system is also great and makes combat more interesting and the hammer is great. Collecting ship parts can be a chore however but it is still good.

10. Pokemon Mystery dungeon Blue Rescue Team - Although the sequel has a longer story, it lacks this one's charm. The friend areas can slow things down but they are each unique and as a result a treat, plus they keep pokemon easy to find. Then this one has many branching out after story quests dealing with legendaries that extend the game play and make for great reasons to keep going after you finish the game. Which makes this one longer and more enjoyable as it answers many questions afterwards, then if you have a ds or ds lite you can even rescue your self if you have the gba version (I never got to try this). Making this the better version and a great ds game.

I hope that helped you find a few, if you want I can suggest maybe another 5 good games that you might like to collect, particularly if you have some of the above.

No real order to mine either.
1) 999
2) Professor Layton and the Unwound Future
3) Professor Layton and the Curious Village
4) Golden Sun Dark Dawn
5) Elite Beat Agents
6) Castlevania: Portrait of Ruin
7) Kirby Super Star Ultra
8) Viewtiful Joe: Double Trouble
9) Pokemon Pearl
10) Kirby Mass Attack

If I could list DSiware games, then I'd probably put on Shantae: Risky's Revenge, Soul of Darkness, Zelda 4 Swords, and Oregon Trail

This could be hard, because my opinions are always changing... Definately no order to this.

1. Mario and Luigi: Partners in Time. Playing through it again right now, and even though alot of people didn't care for it, I love it to death.

2. Mario and Luigi: Bowser's Inside Story. I'm obviously a fan of the series.

3. Pokemon: Black/White. I got White, very addictive (as all Pokemon games seem to be).

4. Super Princess Peach. Not a new concept, but kind of different since Peach is saving Mario. I enjoyed it more than NSMB (not to say it wasn't awesome, though).

5. Animal Crossing: Wild World. I'm a little burnt out now, but I won't lie, got tons of hours into that game.

6. Mario Kart DS. Because back in high school, being the best out of our full crowd of racers was fun.

7. Super Mario 64 DS. First game I got for it, who doesn't love this game?

8. Yoshi's Island DS. Loved the first Yoshi's Island, and this one was almost as fun. Much more frustrating, though.

9. Fire Emblem: Shadow Dragon. Not my favorite FE, but definately is up there for me just because it's from the series.

10. Nintendogs. Yeah, I'm lame.

(in no rating)
the dementium series
super mario 64 ds
the loz games
mario kart
call of duty series
metroid prime hunters
kirby series
animal crossing
ultimate mortal kombat
custom robo arena

1. Professor Layton and The Unwound future- the most touching ending ever.
2. Kingdom hearts 358/2 days- Loved the story, my first KH game too!
3. DQ 9 SotSS- Fun story, played for over 200 hrs.
4 Solatorobo: Red the Hunter- would be higher, but I still have to finish it
5. Animal Crossing WW: Perfect town, all golden tools, tons of playtime, played for a long time!
6. Mario Kart ds- Fun, played for hours.
7. Super Mario 64 ds- never played the original, but loved this game.
8. Scribblenauts/ Super Scribblenauts Loved them both equally!
9. The Legend of Zelda Spirit Tracks- fun, long story.
10. Pokémon Black- Fun game, felt compelled to catch 'em all!

1. Ghost Trick
2. The World ends with You
3. Mario Kart DS
4. Professor Layton and the curious village
5. Shin Megami Tensei- Devil Survivor
6. Okamiden
7. Mario and Luigi : Bowser's inside story
8.Kirby Mass Attack
9. Golden Sun Dark Dawn
10. Tony Hawk's American Skateland (seriously)

Rhythm heaven also belongs in my list above, and TWEWY. Forgot both!

My list on the first page is still the same except replace Kirby with TWEWY.

1. Professor Layton and The Lost Future/Professor Layton and The Unwound Future- The best Layton game yet. A good balance in the challenge of puzzles, great cast, a clever plot and a truly heart-wrenching ending. If you like puzzles this game is a must-own.
2. Pokemon HeartGold or Pokemon SoulSilver- If you ask me, they are better than Black and White by miles. It may just be the nostalgia of these two, but as soon as I finished White which took about three days I picked it up again straight away and I was giddy with happiness. My Pokewalker also recently run out of battery. Plus there is plenty to do when done- tracking phone numbers, training for Red, Pokeathlon, etc.
3. Animal Crossing: Wild World- A gem of a game you will keep coming back to. There is so much to do- you can chat with your villages, hunt all the furniture, catch bugs and fish, fill out your museum- the closest thing to endless content out on DS. I saw someone say, "Animal Crossing is like a vacation everyday"... They are right.
4. Tetris DS- The difficulty is well balanced, the graphic effects are awesomely nostalgic and there is a lot of replay value with the ONLINE MODE. Awesome. The best thing about it is it is portable, it is perfectly suited for a pocket game. (And much better than that crappy Tetris iPhone game lol.)
5. Kirby Mass Attack- A fun game with great extras and tons of replay value.
6. New Super Mario Bros.- Why does everybody seem to say the New Bros. Games sucked? I loved them, this one is much better though, because it's more puzzle-filled and is portable. The VS mode is endlessly amusing as well! Excellent game. But there isn't much to do when you've collected all the Star Coins, unless you feel like maxing out your score or something?
7. Super Mario 64 DS- A classic Mario platformer with upgraded graphics, need I say more?
8. Yoshi's Island DS- Still wondering why everyone hates it, it's very charming, and there are lots of puzzles. But maybe I just love it because I hadn't played the SNES version until just recently when I got it on my 3DS. I'm definitely not the person to ask about it...
9. Mario Kart DS- Good track selection and Mission Mode is fantastic. Just a bit dated now because Mario Kart 7 is out and the online is filled with hackers and annoying snakers().
10. Pokemon Black or Pokemon White- They get the final mention only because they are addictive RPGs with a fantastic story mode but they get boring once you finish the main game because there is nothing left to do unless you are good at competitive battles or can be bothered to sign up for the Dream World.

I wanted to add the some more games from the Layton series, Pokemon Mystery Dungeon and a few others, but they would have taken up more slots and they are not as MEMORABLE as these, I tried to keep this varied as well.

So honorable mentions- The other Layton Games('specially 2 and 4), the Pokemon Mystery Dungeon games, Mario & Luigi: Bowser's Inside Story, The Legend of Starfy/Stafy, The Legend of Spyro: A New Beginning, and on DSiWare- The Legend of Zelda: Four Swords Adventure, Pyoro, and Mario VS Donkey Kong Minis March Again!.

I'll have to rank these in the order of playtime they get, because I play my favorite games the most! Let's look through the 3DS Activity Log:
1) Trackmania Turbo - I can play Trackmania wherever I am!
2) Kirby Super Star Ultra - Best Kirby game ever! 'Nuff said!
3) Pokemon Black Version - Gotta catch 'em all
4) Mario Kart DS - Although Mario Kart 7 is considerably better, I still give a good amount of time to Mario Kart DS.
5) Mario & Luigi: Bowser's Inside Story: Best (and funniest!) RPG I've ever played!
6) New Super Mario Bros. - I am a master of the Mario vs. Luigi mode, and so is my friend with whom I play it with. Good for hours of fun!
7) Plants vs. Zombies - Certainly not the best iteration of PvZ, I like being able to take it with me, and it stands as it's own game pretty well.
8) Super Scribblenauts - The ability to create anything I can think of and see what they do to each other? Sign me up!
9) Tetris Party Deluxe - Gotta have my fill of Tetris every once in a while!
10) Kirby Mass Attack - Lots of Kirbys = lots of fun!

From 10 being least liked to 1 being best, here is my list:
10.Need For Speed Carbon
9:.Need for Speed Pro Street
8.Fossil Fighters
7.Spectrobes
6.Spectrobes Beyond The Portals
5.Pokemon Diamond
4.Pokemon White
3.Pokemon Platinum
2.Pokemon Heartgold
1.Mario Kart DS

1) Shin Megami Tensei: Strange Journey
2)Radiant Historia
3)Pokemon White
4)Shin Megami Tensei: Devil Survivor 2
5)Dragon Ball Z: Attack of the Saiyans
6)Dementium: The Ward
7)Chrono Trigger DS
8)Shin Megami Tensei: Devil Survivor
9)Solatorobo
10)Etrian Odyssey 3

My DS favorites in no specific order :

-New Super Mario Bros.
-Nintendogs
-Animal Crossing : Wild World
-Mario Kart DS
-Rhythm Heaven
-Kirby Super Star Ultra
-Pokemon Diamond / Pearl
-Pokemon Black / White
-The Legend of Zelda Phantom Hourglass
-Final Fantasy Tactics A2 Grimoire of the Rift