To me New Super Mario Bros Wii is the best by far! I remember playing it some years ago with some friends. We didn't sleep that night... and we finished the game!. We did miss all the optionals but it was damn fun!

NSMB DS was the first real 2D Mario with tight controls (doesn't count Land or 6 Golden Coins) since SMW in 1991, so that was a great experience. Nowadays NSMBDS feels actually a little "buggy" if you play it after you played the later ones :P But it's still one of my favourites of the New's.

NSMB Wii had a little loose controls, not nearly as bad as Little Big Planet, but it just felt more realistic and less like Mario in my opinion... The level design was really bland as well.

NSMB 2 is the absolute worst of the bunch. No creativity whatsoever, except for some of the stages in level design. I mean, they reused the WHOLE soundtrack of the previous game! Except for the special world map themes, but they weren't anything special either :P

NSMB U is a little better, but it set my Mario fatigue in stone. I personally don't want another 2D Mario until late next gen at the earliest. Even then I think I'll be bored. At least they changed some of the assets, backgrounds and stuff.

NSLU is a whole lot more fresh than NSMB has been since DS. The controls feels more dangerous and more aimed at pro players.

Still NSMB DS is the best for me personally. How could Nintendo forget the terrific multiplayer in later games? I mean the co op is the whole point of U and Wii, but the small battle stages were really great with stars collecting. Reminds me a little bit of the MKDS days... Block Fort <3

I guess technically NSMBU would be the best one and the one to buy but you never forget your "first". Playing NSMB on DS was like catching up with an old friend.

"Hey, 2D Mario! I missed you!"
"You got a divorce?"
"And how are the kids?"
"Remember when we used to watch each other take a shit? That was crazy!"

By the time NSMBU rolled out, I was ready for 2D Mario to go back home.

definitely NSMBU

NSMBU > NSMB Wii > NSMB 2 > NSMB

U > Wii > B2 >>>>>B

NSMBU is the best, though it has suffered from fatigue. The level design was top notch, and had me enjoying the game despite it not being long enough since the last NSMB entry being released.

However, the multiplayer game in NSMBDS is hands down, one of the best multiplayer games I have ever played. The castle level made for the best tactics as well.

NSMB for DS.

All have better and worse parts, but they're all pretty equal. Haven't played NSMB2 though.

my favorite is NSMB DS solely because of the Mario Vs. Luigi mode