Little Mac, Tingle, Skull Kid, Mega Man, Geno, Neku, Chunky Kong, Chris Redfeild, Dixie Kong, Mii, Ryu, Chun-Li, Little King, Travis Touchdown, Jack (Madworld), Sora, Roxas, Ninten, Roy, Bill Razor, Chibarasu.

Bosses Mother Brain, 02, King K rool, exor, Vatti, Yami, Fawful, Medusa, Morphia, Girantina, Regigigas, Black Barren
Enemies Octorock, Stalfoes, Kremlings, Tikis, Burnto Bert, Pokey, New age Retro Hippie, Eggplant Wizard, Chus, Spearow, Heartless, Death watch contestants.

Lucas is completely different from Ness.Different melee attack, up and down smashs and specials. His PK Fire goes goes in a traight line and creates an angled pillar when he hits an enemy. His PK thunder is slower, his PK magnet sticks out (and another thing but i wont tell you ), and his B move is PK Freeze, not flash, which goes slower and just damages the enemy.

Mega Man, Crono, Neku (from The World Ends with You), Zero, Proto Man, Bass, Fawful, and the dog from Duck Hunt so I can finally beat him up!

This guy,

and these guys.

Edit: what about her. Queen Koopa!

I'm not sure if anyone has suggested this yet.. but I would like Mii compatibility. Also, would like to see Funky Kong included (possibly as an alt costume for DK) and Dry Bowser (alt costume for bowser)

As for a real character.. Koopa Troopa

I want to see professor layton and the guy from scribbelnauts!!! I want to see sonic , and I want to see toad, come on toad is awesome!!!

This Guy:

This one had a missed opportunity with midna, I really hoped she would make it... Toads would be fun too, or being a boo, or petey piranha

Mega Man characters.
MM>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>Sonic

Mewtwo - Give him back, come on, it's the coolest Pokémon ever and the only one that has at least a minimal amount of backstory..
King K. Rool - think about all the possibilities with different costumes!
Fawful - Need I say more?
Ridley - If it's somehow possible... He wasn't that big in Metroid/Super Metroid and he's the only other Metroid character I can think of to be important enough to be implemented.

This game needs more villains

Paper Mario and Chibi Robo would be cool, too.

I want King K. Rool in the next one, but since he's not coming back in Donkey Kong Country Returns, I'm afraid that hurts his chances. Miis would be great to have included.

ummm... CommanderVideo and ... Joanna Dark

Geno (Super Mario RPG)
Banjo-Kazooie (I know, I know, it won't happen)
Mega Man
Little Mac
Skull Kid
Bomberman
Chibi-Robo
Ninten

And that's all I can think of.

Bomberman, Toad, Boo, Paper Mario, Sonic, Fawful, a green and poisonous toad.

Dark Force (Dream Land 2 final boss version)

Captain N and Chuck Norris. Mr T would rock as well

Magikarp... to Replace Goldeen (Never said Playable) and Girantina
also Ouendan Level, Wuhu Island, Photo Dojo Level.

CommanderVideo in Smash Bros...wow, that would be epic.

I would like Isaac ,from Golden Sun, to be in the next Super Smash Bros. game!
http://goldensun.neoseeker.com/w/i/goldensun/f/fe/250px-Gs-is...
Picture of him in link above if the picture doesn't show up.

LMFAO... that made my day.
But in all seriousness, I think any of the Castlevania characters / enemies would be sweet.