Megaman for sure if it were a Legends game or something in the same style. I wouldn't like to see another 2d platformer... or even 3d at this point. Something action adventure/action rpg would be great to see on a Nintendo console which they could easily do with Megaman and would fit well with their already existing IP.
I could also totally see a Castlevania reboot with gameplay similar to Lords of the Fallen being a good choice. More mature and at the same time sort of kid friendly(castlevania). I know a lot of people have a hard-on for Bayonetta, but I doubt the bondage chick will continue to be a Nintendo exclusive.
“What I say is, a town isn't a town without a bookstore. It may call itself a town, but unless it's got a bookstore it knows it's not fooling a soul.” - Neil Gaiman
