With my caveat being threefold:
1. I didn't play every game that came out this year (obviously), so you can pretty much rule out sports games and lots and lots of those hyped highbrow 300 hour JRPGs. I also did a crappy job of playing games that came out before the launch of Warhammer, though many of those I don't even believe were contenders.
2. I still don't like some games that everyone else loves, so as much as I wanted to like it, or as badass as the soundtrack was, GTAIV is not on this list. (Other noteworthy absences: Fallout 3 = Oblivion, Fable II = Would have been #11)
3. I'm not going to factor any game I'm involved in (Warhammer) or any direct competitor (Conan, WotLK, Mines of Moria).
And with that out of the way. I shall commence listing.
10. Mirror's Edge - I know I'm in the minority when it comes to Mirror's Edge. And I understand the flaws, I really do. But to me, as an experience, Mirror's Edge is sublime. Visual and visceral, it had some of the most thrilling gameplay I experienced all year. And I believe that any game that moves gameplay and game discussion forward deserves to be elevated above some of its faults.
9. Left 4 Dead - I was late to the L4D bandwagon, which is probably the only explanation on why it's so far down the list. As far as unique experiences go, Left 4 Dead fires on all cylinders. But considering you'll want to play with your friends and probably not random Xbox Live dewds, it places a slightly higher barrier to entry than I would like. Still those moments, when your team has huddled together to make the last stand against the zombie horde, those moments are pure exhilaration.
8. Professor Layton and the Curious Village - At first I thought Professor Layton was a kid's game, until I spotted the review over at GameSpot. Though it contains a number of classic riddles and puzzles (those with a penchant for moving matchsticks will recognize more than a few) it has more than enough to make up for any you might be familiar with. It's the perfect DS game, easy bite-sized pieces, and it goes out of its way to give you plenty of outs if you're stuck.
7. Banjo-Kazooie: Nuts and Bolts - Umm where did this come from? I almost didn't pick up Nuts and Bolts because it seems like every platformer these days churns out a racing game just to make a buck. But this is not just a racing game, and in fact, the racing is the least interesting part. Part cart-building and all-collection, Banjo Kazooie infuses the charm of the first two games into another version that is as every bit a classic, and not even nearly as tedious.
6. World of Goo - Physics games are awesome, but World of Goo isn't just about physics. The puzzles themselves are great, but it's the OCD mode that really takes it to the next level. While each puzzle is beatable with some leeway, OCD often requires that you bend your mind a different way. And the Tower of Goo mode with the floating clouds of other people's heights is pure competition genius.
5. Dead Space - One hour in, I wasn't sure what to make of Dead Space. It was atmospheric, yes. It felt really good, yes. The UI was awesome (and I'm not just saying that because it's Dino). The sound was out of this world...literally. But it took me a couple hours to truly love it. It was nuanced, it was scary, I even liked that it got a little predictable. (Oh something is definitely jumping out of there). But above all, it was fun. Really really fun, the entire time I was playing it. And that's all that matters, yes?
4. Braid - Not sure that Braid needs any more love at this point, so I'm going to forgo talking about how awesome it is and talk about the one thing that I thought was dumb. The ending. No, not the ending, but the part after with all the exposition. Ruined the whole thing for me. I wished they had stopped at the "in reverse" sequence. Everything else was tops.
3. Little Big Planet - If LBP hadn't blown the first week it was out, it might have changed the way people play games. For that matter, if more people owned PS3s, it might change the way people play games. Either way, it's adorable, lovable, endearing, and I want to take a little sackboy around with me everywhere I go, because I love to see him smile. And OMG do I HATE to see him sad.
2. MGS4 - It may come as a surprise that MGS4 isn't my number 1, but it isn't because my number 1 had more diversity. MGS4 is the finest, most beautiful, most storyriffic game that has come out in a long time. It is epic, it is emotional, and above all, it's a big fat pile of Carrie-fan service, that I've been waiting for since the original Metal Gear Solid. So thanks for that Hideo Kojima. Way to go out with a bang.
1. Gears of War 2 - Gears of War 2 is the best example of a sequel that I can think of. More. And more of the stuff you want. More levels with awesome Gears of War content. More co-op levels. More cogtags to collect. More CHAINSAW. But where it excels the most, and honestly the reason I think of it as my favorite game of this year, is Horde mode. I've played it a lot, and it is awesome in every way. And they didn't even have to do it, it's just delicious icing on the top.