Sorry for bumping an old thread.
I too love Mario in 2d, and yes I've enjoyed NSMB2 on 3ds immensely. I just don't get what people don't like about it - it's the best 2d platformer, and 2d platformer is my favourite genre.
Also, the new downloadable levels in NSMB2 are super challenging. In fact harder than Super Meat Boy.
Additionally, the sales of 2D Mario games are much higher than of other games, so Nintendo knows this too.
I'm getting Wii U only to play NSMB U!