MGS Peace Walker no competition.

Yakuza 3, Demons Souls...what? They only came out this year for the EU so they count right?

For me it would be:

Super Mario Galaxy 2 - A fun and ambitious challenge! Couldn't stop reaching for the stars.

Monster Hunter Tri - Talking about fun challenges.

God of War III - Epic and impressive game.

Final Fantasy XIII - Though I still haven't finished it and though I see why it was so critized, I do believe its an outstanding game, impressive in every aspect.

I haven't played Red Dead Redemption yet, but I guess it would be listed here too, and though I don't own an X360, I can see why some people would list Mass Effect 2 and Alan Wake. In the end, though, I guess my choice would be Super Mario Galaxy 2. Just to show Nintendo some love.

RdR

Mass Effect 2

Super Mario Galaxy, Mass Effect 2 and God of War III for obvious reasons. Then there's Heavy Rain, Red Dead Redemption and Bayonetta that could have a shot. Final Fantasy XIII was rated too low but I suppose even it will get some awards. Then there could be some Wii games I barely even know, as well as handheld games. Oh, Metal Gear Solid: Peace Walker could be the best PSP game.

As for my personal opinion, so far I'd give it to Final Fantasy XIII. I just could stop playing until I finished it (unlike many others who couldn't press on to continue playing).

Pokemon HeartGold and SoulSilver

I have never been more content with a Pokemon game. All the innovations of the games since G/S originally came out are here plus tons of new extras like being able to re-battle Gym Leaders, new areas to explore and even more Pokemon to collect. My sister and I have been playing HeartGold and SoulSilver (respectively) and combined we have over 400 hours clocked.

God of War III- The presentation and the way it seamlessly blends storytelling and epic battle scenes perfectly together. Jaw dropping visuals and it showed why anyone really should buy a PS3.

Mass Effect 2- The first Mass Effect was a good game marred by technical problems. Mass Effect 2 takes an interesting and unique concept and completely revamps it for a better, stable gameplay. The Story is amazing, the characters are fantastic and the gameplay has made me come back and play Mass Effect 2 over and over and over again.

PS3: Final Fantasy XIII followed by God of War III

Wii: Super Mario Galaxy 2

PC: Starcraft II beta (yes it counts!)

Mass Effect 2 and God of War III were the most impressive from what I've played sofar, with MGS Peace Walker comming close.

But the first half of the year doesn't matter one bit with Starcraft II, Civ V and GT5 around the corner...

Super Mario Galaxy 2 has to be the frontrunner.  The reason being is that it does a little bit of everything that's been done in any Mario game ever.  It appeals to the nostalgic Mario fan, regardless of whether the first Mario game you played was Super Mario Bros. or Super Mario Galaxy  

The game that I personally have enjoyed the most is Monster Hunter Tri.  It has just as much replay value as any game that I've ever played.  It won't be up for any game of the year honors because I don't work for the media.