Most Played
Battlefield: Bad Company 2 on the Xbox 360. I got my Xbox 360 back in February, and it was the Modern Warfare 2 edition. I played the fuck out of it, and I loved the multiplayer, but when Bad Company 2 was released, it just faded out. So many great matches with friends, so many awesome memories. No matter how much the single player sucked, nothing could dethrone it, and now that Vietnam was released, I doubt that anything will for some time.
Yeah, this impressed me
This also goes to Battlefield: Bad Company 2 on the Xbox 360, because I didn't even know about the game before I saw the multiplayer demo in Xbox Live Arcade and decided to check it out due to general boredom. So, from a title that in January wouldn't have ringed any bells to a must-prepurchase and the multiplayer game of the year.
Most disappointed with
An older title I had always heard about but never played, a friend of mine finally made me get a copy of Dead Rising on the Xbox 360. Pumped up for loads of zombie splattering fun, instead I got a tightly timed, boring tunnel run. Needless to say my disappointment was great.
Better than expected
When I purchased Dead Space for the PC a year ago, I didn't even bother to really get started due to twitchy frame rates and jerky mouse movement. I decided to give it an another shot on the 360, and oh boy. It pretty much provided me with one of the greatest single player experiences of the last decade. It's not like I expected the game to be bad or anything, but since the PC experience was such a lackluster, I went into the 360 version not expecting much, and was duly surprised. ... yeah, Dead Space on the Xbox 360.
Honorable mention
One only? Fuck that. Left 4 Dead 2 on the PC kept me amused for a lot of the year especially after Realism Versus was launched. Company of Heroes on the PC is always fun to play with a bunch of friends. Call of Duty: Modern Warfare 2 on the Xbox 360 did take a lot of my Xbox time in the start... and then finally there's Mass Effect 2 on the PC, which was awesome beyond belief.