Find your niche.
Man I don't have NSMB2, so I don't know how good it is. At least I think the coin abundance was an interesting gimmick. I just love the concept of golden fireballs that can turn stuff into coins, plus having so many coins to collect and a counter specifically for that. The coin collecting and 1-UP sound effects have always been music to my ears. In fact, if coins had more of a use than a simple score counter and 1-UP giver like getting to unlock cool stuff (like Temple Run, I guess) then that would be sweet (or do they have that already? I'm too lazy to check. :P ). However, I can see how the abundance it gives you tons and tons of lives (assuming the 1-UP rule for a hundred coins stuck even for such a game) which tempers down the difficulty. :( I wish the New Super Mario Bros series of games would get a little more creative in different ways, perhaps adding new playable characters, a new setting, an actual plot or completely new villains, something like that. Gameplay-wise, I have no idea if the stuff they brought back and added to NSMB2 was particularly great, but I'm sure it was still fun to play.
Haven't played 3D Land either, so I still can't relate. I think I would love to have that game, though. It looks fun, and I hear it is, too. And I'm really curious with how well the 2D and 3D styles mash together.