I'd like to see a new 2D Mario platformer, still SMG is pretty awsome also, I might get a Wii just for that game when it comes down in price, but a nice 2D Mario would be great.
My favorite games for this gen:
1. Gears of War 2. MGS4 3. Killzone 2 4. Halo 3(Underated by many) 5. Mass Effect