Runner 2 is pretty fun. Although since virtual console came out, I would say that Super mario world is the best game you could ever possibly right now. That might change in the future. I would reccomend The Cave but I've actually never played it. Do you guys know if it's any good?
Oh shit, I forgot about The Cave. I recommend that one, too. It's a fun puzzle-platformer. Not mind-numbingly difficult, but the stories of the individual characters, coupled with the humor of The Cave (which narrates as you go), make it all worthwhile.