There were a lot of well-regarded games that I won't manage to play before the end of the year, but of what I have played, three games stand out:
Journey was such a unique experience with great visual aesthetics, music, and a really novel approach to multiplayer. I went into the game blind, just based on my affection for the studio's past work, and wasn't even 100% certain that it was a multiplayer game until the reveal at the end. Also, the way that the (admittedly simple) gameplay mechanics are discovered purely through play, and not through any sort of tutorial, really increased the sense of immersion into the game universe.
XCOM was a game that I would have enjoyed even if the execution was extremely flawed, since I'm such a huge fan of the genre and since the genre has seen so few entries in recent years, especially on the scale of this. Prior to PAX East, I was expecting a half-hearted effort, and would have been happy to have it. After seeing Firaxis' booth demo and sitting in on their panel at Pax East, I was sold on the development team's vision, and was much more enthusiastic about the game. The execution was still a question mark, but once I got my hands on the actual game, I was blown away. I have been waiting over a decade for a turn-based squad tactics game to pick up where Jagged Alliance 2 left off, and I finally have it. I hope to god the game has sold well, because I would love to see this genre come back. Even if it doesn't, though, I've got an awesome game I'll be playing for years.
It feels kind of awkward heaping a bunch of praise on the The Walking Dead on Idle Thumbs, because it's in very large part Jake and Sean's game, but god damn, I don't know that I've ever had this level of narrative buy-in in any work of fiction. Games have an inherent advantage over literature and film in that the player has agency over the actions of the protagonist, but I can't think of any other game I've played that has leveraged that fact as well in service of the narrative. Which is remarkable, because as gut-wrenching and immediate as the decisions you're faced with are, their impact on the over-arching narrative seems largely illusory. But it works, completely. Hats off to those guys. On top of that, I've started reading the Kirkman comics since playing the game (never seen the show), and the degree to which the universe feels of a part across both mediums in incredible. That's quite an accomplishment in and of itself.