I've never kept a note of the games I finish in one year before but I intend to do so this year. Here's what I've finished so far:

Fallout 3: Broken Steel DLC (360)

House of the Dead Overkill (Wii)

Dead Rising: Chop Till You Drop (Wii)

Resident Evil 5 (360)

Gears of War (360)

Bioshock (360)

Fight Night Round 3 (360)

Ironman (360)

CSI: Hard Evidence (360)

Kameo Elements of Power (360)

Call of Duty: World at War (360)

Fallout 3: Operation Anchorage DLC (360)

My definition of "finish" is simply to have finished the main single player mode. There's very few games I try to get 100% on, but there are exceptions:

It's GTA IV, for anyone who hasn't played it. Now I've got the DLC for that to complete as well...