For me a toss up between Kirby's Epic Yarn and Motorstorm Apocalypse.
My mate and I sat a played Kirby straight away and had a blast, I fucking loved grieving him by throwing him of ledges and to the left of the screen :P!
Motorstorm blew me away! I've never really been for 3D, played Killzone 3 and felt underwhelmed (by the 3D, not the game... JETPACK = AWESOME). But I sat down to play the newly unveiled level of Motorstorm (shown at the panel) and the 3D effects were so cool, my favourite being smoke that seemed to cloud your vision!