LittleBigPlanet - absolutely loved the beta. what people came up with in a limited period of time with a sample of the full toolset was very impressive. The story mode seems to be nicely flushed out and co-op gameplay just makes you smile.
I was going to buy World of Goo (PC) but reconsidered just based on how many games I have in my backlog.
Demon's Souls Official Thread | Currently playing: Left 4 Dead 2, LittleBigPlanet 2, Magicka