Super Paper Mario might've been the happiest game at the Nintendo booth at GDC. This 2D/3D platformer features a lot of character and charm, something the Paper Mario series has been known for. This ex-Gamecube title gathered the largest crowds and lines at Nintendo's booth, and it's clear why: it's simply a lot of fun.
You hold the Wii Remote sideways, in classic NES form. Because the game plays homage to the early 2D Mario platformers, the Wii Remote may actually be superior than the Gamecube controller for this game. The D-Pad obviously moves the character, while 1 and 2 allow you to do the basics, like Jump. The game's unique feature, dimension changing, comes through the use of the A button. By simply hitting A, the game world rotates, revealing depth to Mario's once flat world.
Even without the dimension-shifting mechanic, Super Paper Mario would've been a fun and imaginative game. There are tons of environmental effects that take Mario to new, surprising places. Also, you'll finally be able to play as multiple characters, such as Peach. With her parasol in hand, you'll be able to go far distances, a la Super Mario Bros. 2. Also, although the game doesn't feature any significant Wii enhancements, it's nice to see the game running in widescreen and in 480p. The game might not feature any truly spectacular graphics, but the playful paper art style still looks great. Definitely keep an eye out for this one when it comes out in April.