This year:
1) Brawl. I'm a huge Nintendo fan, and this is the most balanced yet strategic fighting game I've ever played. Hell, you can even use the randomness as an advantage XD
2) Left 4 Dead. The AI director is just FANTASTIC! And the gameplay is something different than your typical FPS fare--very refreshing.
3) Gears of War 2. I loved the original, and this one just beats it in every possible way. THE HORDE!!
Handheld:
(haven't played very many)
Professor Layton and the Curious Village. Beautiful graphics, nice fatherly voice for the good professor, and of course highly challenging puzzles.
Other Year:
Elite Beat Agents. 'nuff said.