Vote for your favorite!
Blast Works: Build, Trade, Destroy
Braid
Korg DS-10
Left 4 Dead
LittleBigPlanet
Mirror's Edge
Shin Megami Tensei: Persona 4
Wii Fit
World Ends With You, The
World of Goo
Wii Fit. It's not the best "game" ever, but it helped bringing new people into gaming.