I might get attacked for this, but IMO, 2006 was a down year for games, maybe due to the fact that a lot of time was spent on Wii and PS3 rather than on the games. That being said, there were some great games released. But I am really looking forward to 2007, which as of now looks to have a handful of excellent releases.
For 2006, I didn't buy too many games, but I have to rate Zelda: Twilight Princess as my favorite one.
My list for most anticipated releases in 2007 is:
1. Assassin's Creed: looks incredible! It may end up being one of the greatest games ever created IMO.
2. Super Mario Galaxy
3. Devil May Cry - who doesn't want to see the sequel?
4. Prince of Persia 4...?