For me personally this year has been kind of...disappointing isn't the right word, but there haven't been very many games that really excited me. So I've only given two titles any serious consideration as game of the year.
The first is Mass Effect 2.
The sequel to one of my favorite games ever, and a new entry into what is very quickly becoming my favorite science fiction franchise. As anyone who posted in the Mass Effect 2 thread can attest, I was highly skeptical of the changes Bioware was making, and that's putting it rather mildly. But as usual, Bioware knows best, because they took what was broken in the first game, and not only made it work, but made it a lot of fun and quite possibly took a revolutionary new step forward for RPGs in the process.
The other game is Red Dead Redemption.
Better in every way than their seminal Grand Theft Auto series, Rockstar really outdid themselves with this game. The old west is a setting that seems perfect for video games, and many developers have tried and subsequently failed at trying to capture it. Rockstar on the hand stepped up to the plate and knocked it out of the ****ing park. With Red Dead Redemption they crafted a powerful story filled with interesting and memorable characters and set it in an incredibly beautiful world.
It's a really tough decision for me since they were both so great, but I have to go with my instinct and say Mass Effect.
It's probably not fair for Red Dead Redemption since Mass Effect 2 is an extension of a game and a universe that I already loved...a lot, and for all intents and purposes Red Dead is largely a brand new IP. But that's just the way the cookie crumbles. C'est la vie.