New Super Mario Bros. 2
So, is it any good? I absolutely loved the predecessor, and I need a good 2D-platformer for my 3DS. I've heard that it's a massive coinfest void of any challenge whatsoever, so if any of you've played it, tell me what you think.
I was wondering the same thing. I've also heard the same exact things as well. That's how Super Mario 3D Land turned out to be (I'm very glad I got that game for free :D).

If you're looking for a cheap 2D platformer that's also good, get Gunman Clive from the eShop. Why?

-It is Megaman in the Wild West.
-It is a 2D platformer
-It can be a challenge (What? A challenging gaem in the eight generation?!)

Most importantly:
-It is $2 (£1.29 for all you in the UK, I think)
It's pretty much exactly the same as the previous games, but with coins.
Ridiculously easy, same music, same everything, different levels.

It is good of course, it's still a Mario game, but you're gonna feel you've played it before.
Of all NSMB games, I enjoyed this one the least. I really loved NSMBU though.
From what I remember, some of the star coins in NSMB were really hard to find because of hidden entrances in ghost mansions and such, and some of the later levels were pretty tricky.