Spore. After a couple years of promotion, the game turned out to be remarkably boring, especially when going into the space stage.
SimCity Societies. Really, EA? Your answer to the user's requests to have the ability to make a perfect, realistic 3D city is to give us gingerbread houses and candy cane light poles? Seriously?
I did, however, like both Fallout 3 and Bioshock.