I actually think I will award Arkham City Game of the Year 2011 (though I'm prepared to omit Skyrim from this as I still have SO much to experience there).
It's a phenomenal piece of work - it's incredibly well polished, pretty big, amazing fight scenes, engaging story and - above all - FUN. This is exactly what game developers need to be doing. I've not played any side quest or even main quest that hasn't been brilliant. Oh, and the gadgets. And the characters. And the stealth modes. And the Catwoman missions.
It's incredible, bettering the original in every single way. Quite a feat considering Arkham Asylum is one of my top 10 games ever. Arkham City will probably make my top 5.