This is the retro forum, so I'm going to say Gameboy Tetris or Tengen Tetris for the NES, although I mainly play Tetris DS these days.

I would have to say Tetris DS for now. I may be buying Tetris DX soon for GBC. I do have Magical Tetris Challenge but I'm not sure if anyone remember or knows that one. I'm thinking about getting Tetris Party for Wii. Sounds like a good game to play with my g/f.

Tetris DS is for me the complete package, lots of game modes and wifi VS, it's almost perfect.

except for infinate spin!

I have only played the NES version of Tetris, and the PC Freeware one which I have on my computer that I play whenever I'm bored.

Tetris DS all the way! I just love the old school nintendo themes!

Tetris Plus on Playstation. Haven't played Tetris DS.

It probably won't happen, but I hope they put the NES version of Tetris on the VC, it has my favorite music, the 3rd one. With that said, Tetris DS and Tetris party are both awesome, and worth the money for any Tetris lover.

Tetris is my favorite game of all time. Over the years, I've played Tetris on the NES, SNES, GB, VB, GBA, NDS, N64, GC, Wii, cell phone, and arcade. Here are my top 4, in order of preference:
#1 - Tetris DX
#2 - Tetris DS
#3 - Tetris (nes)
#4 - The New Tetris (N64)

Among the versions I played, Tetris DS is the best one. It gets really fast and responsive and that's the most important thing in multiplayer. Cool online, ranking system was great... Too bad for cheaters you can find =/ On single player it offers a lot of interesting spin-outs, so Tetris DS is definitely a winner.
Another version I loved is The New Tetris, but I haven't the original N64 cartridge, so I hope it gets released on the VC someday. The 4x4 blocks added a lot of spice and actually revolutionized the way you play Tetris. Besides Marathon, the other modes offered quite a challenge for High Scores maniacs!
I downloaded Tetris Party but it was almost a delusion... It's pretty sloppy, it makes you lose the right rythm when things get heated. Additional modes aren't that great, either. At least they put up the tourneys, so I could win a lot of free Wii Points =D

Anyway, I guess the best versions are the Grandmaster ones, but I never had the chance to play any of those =/

Tetris DS is the definitive falling block experience dethroning the reigning champion Gameboy Tetris. Other runners up include NES Tetris, the original PC Tetris, and Tetris Worlds