Super Mario 644. That's all I'm gonna say.
I'm also just going to throw this out- Nintendo has had pretty much a year, not counting Skyward Sword, of no "major" console game releases. Yeah, yeah, Mario Party 9 (also Kirby's Adventure, which I am ashamed to throw under the bus), but they've used the Rainfall games to buffer the end of the Wii lifetime for pretty much a whole year. They've been working on things for the Wii U and they damn well better show it off next week. They better understand that this presentation can't be half-assed if they're going to sell this system, and personally, I buy Nintendo systems primarily for Nintendo games, so SHOW ME THEM.