Catherine. Unquestionably Catherine.
I knew Deus Ex: HR would be good, I know Zelda and Skyrim will be great, I knew Portal 2 would be a sensation, but I had no clue I'd fall in love with Catherine so helplessly. I love the way the story propelled me to engage with its thematically appropriate gameplay, it had the best localization of any game I've ever played, it explored its theme front to back, its characters felt so real...and it was refreshingly tough in the right ways!
I haven't played a game with the tungsten balls that Catherine had since Killer7. I'm so glad it paid off for Atlus; their best selling game was a psychosexual block puzzler that deconstructs "love." It was a happy occurrence for those who wanted something bold and new, it's my game of this year, and it is on my top 10 of all time.