1. XCOM: Enemy Unknown
I feared the worst, I hoped for the best. I was so excited for XCOM to finally hit, and when it did, I and tons of friends were completely sucked in for weeks. There are very few games that hit this level of design. It's fantastically well made, and if it wasn't for some lacklustre art, a few bugs and a few mechanical choices, I'd want to call it perfect. As it is, I don't think we could have gotten a better XCOM remake. It is absolutely the best game of 2012, hands down.
2. Crusader Kings II
I've always had an affinity for large-scale map-based strategy, but the dryness of "crush all your faceless opponents" doesn't hold my attention for that long anymore. CK2 is basically The Sims, but in late medieval Europe, with lives and land at stake, and somehow it works brilliantly at it. I end up legitimately invested in whether or not I end up the Duke of Whatever after my massive plot is sprung against the existing Duke, betrayed if my cousin rises up from some distant province to take me down. It feels like one of the best implementations of what Paradox started with Europa Universalis 1 - finally all the little event popups and sliders start to take on some personality. It's a great, addictive, totally weird game.
3. PlanetSide 2
I didn't expect this to grab me, but the combination of utterly beautiful landscapes, with BF3-style massively-multiplayer warfare that actually works(!!) has led to me spending dozens of hours with it already, and despite thinking I never would, I've now finally put money into an F2P game. And it felt totally worth it.
4. Magic: The Gathering - Duels of the Planeswalkers 2013
This is another entry in a series that looks like it's going to be annualized like a sports game. I didn't know what to expect from it - I was vaguely familiar with Magic from when I was 13 and bought some and my friends and I half-assedly tried to play it - but it's got a great difficulty ramp-up, a really clear interface, and pretty good AI. I blew threw the whole thing and wanted more when I was done.
5. Torchlight II
I played a lot of Torchlight II. I played a lot of Diablo III, too, but what I really should have been playing was Torchlight II. It was the game I wanted, and every well-tuned mechanic made me grin about the fact that Runic is able to make these games the right way. There's a great interplay of systems going on in TL2 that make it really hard to stop playing. That voice acting was TERRIBLE though, wow. Oh well.
6. Legend of Grimrock
The Grimrock devs locked themselves in a time capsule and emerged in 2012 with a totally fun, first-person dungeon crawler. In 2012! What!
7. Hotline Miami
It might not be the most technically brilliant game, but if more games had this much style I'd be way into it.