I would have to say mine is New Super Mario Bros. U

I would agree simply because the first on the DS was disappointingly bland, the second on the Wii insisted on using waggle moves, which instantly ruined the game for me, and U has better level design than 2.

NSMBU, it really was a great game, just didn't have the wow factor which was a shame since it was the best in the series

I've only played the first three, and out of them the second felt the best, the one on the Wii.

I prefer NSMB Wii. I felt NSMB U was a bit bland compared to the Wii, as well the power ups were boring/uncreative and the mini games to get more 1ups/power ups were boring.

NSMBU > NSMBWii > NSMB > NSMB2

I enjoyed the Wii u one the most, closely followed by the ds one. Nothing comes close to the older games though especially SMW and SMB 3, now those were damn good games.

NSMB U has the best graphics and is the most techincally impressive, it has a few really clever levels and it is in general a very good game.

But to me, NSMB Wii was the best game in general. It had that special status of being the first 2D Mario on a home console since 1991, and it was also the first Mario game to have the Koopa Kids back in it. It honestly felt like the closest thing to an honest to god "Super Mario Bros. 5". Plus, it just had great level design (to me), it had the best power ups of the series, most especially the Penguin Suit which is arguably the most useful and coolest power up this side of the SMB3 Tanooki Suit. And the item inventory system was fantastically set up, whereas the NSMBU power up inventory was very limited.

So yeah, all around, I'd have to say NSMB Wii is the best of the series.

I'm in the vast minority (knowingly), but I would have to say NSMB 2 (by a hair). I own and have played a good amount of all 4, but I've only beaten the DS and 3DS versions. To me, the multiplayer focus of the Wii and Wii U games makes the levels feel too open and empty when playing single-player, and personally I found the multiplayer to be borderline terrible. The handheld versions however just feel "right" to me…with the camera zoomed in a bit more so there's no "empty" feeling. The NSMB series in general, in my opinion, is lazy. They've recycled the same world themes, the same damn music (an unforgivable sin given the talent of Nintendo's various music teams), and the art design and graphics just seem half-assed. The DS game was a novelty when it first came out cause it had been so long. The other three are aggravatingly redundant. However, I can almost forgive both of the handheld versions because the series feels more "at home" there. If they were to try and be creative and go in a new direction with the level designs, or art style, or music, or graphics…THEN it'd be okay to make console NSMB games. The way they are though…there isn't an appropriate amount of effort put in for the console ones. Handhelds, with lower system specs and the cheaper price point is more acceptable. This is long-winded, sorry…basically I only like the DS and 3DS versions and of those two I like NSMB 2 slightly more just because it looks nicer and I love 3DS, so I'm biased. :p

One of the first two...
NSMB was great on the go...
NSMBW was great with friends...
NSMB2 was okay...
NSMBU and NSL came too soon after NSMB2; I thought it was a chore to get through the both of them...
I probably would have liked NSMBU more if I played it with friends...