Voted for The Walking Dead, XCOM and Dishonored myself.
The Walking Dead was outstanding storytelling and as Gamasutra agrees, a complete step up for the point-and-click adventure game genre.
XCOM had the most fun, punchy gameplay this year. I couldn't believe while playing it that this is a modern, 2012 game - tactical turn-based games can still be made in this day and age, who would've thought!
Dishonored had amazing art and immersiveness, and the gameplay was pretty good. My only problem with it is that the story turns out a bit disappointing, and you sort of hit a plateau so that you aren't ever further challenged - a shame considering its influences Deus Ex and Thief were intelligent at upping the ante and leaving you a bit short-handed.