Let's see...
1: SCV: There character creation is still lasting me even today. The game itself has its off-and-ons, but I still play it more frequently than any other game I own to this day.
2: Minecraft Xbox 360 Edition: Played it for many, many, many, many hours, with and without friends... We've made giant trees, towers, volcanoes, castles and lots of other excellent and astonishing things!
3: I dunno... other than SCV, it's not been a great year for me. I suppose I'd have to say Dragon's Dogma. Playing it with friends felt very involving despite it being single player. It was also bloody OK, it was.
4: Borderlands 2? It's alright I suppose. Gets repetitive after a while as the first did, but, while initially all the characters felt varied and interesting the more i played with each the less i liked them, except Salvador.
5: erm... ... ... Oh, Xbox 360 Minecraft! gotta reorder!
errrr...
I'm not sure i've even played any other 2012 games... I suppose I rented ME3, but I really did not like that, so...
What about PSAS:BR? It was a good effort that I do like, but it hasn't held my attention and it's buggy as hell.