I can't believe I didn't even post a placeholder here...but anyway, I'll get to it. I only track new completions (or games that I get all the achievements in...yes, I'm a whore), so this list will be missing anything I've beaten in the past, so this isn't everything I've beat this year, only what I've beat for the first time.
January:
Monopoly (SNES) - Finished a game against the maximum number of CPU players.
NHL '97 (SNES) - Okay, so I simmed the season, but I played through the playoffs and won the Stanley Cup.
The Chessmaster (SNES) - Beat the computer on the default settings.
Caesar's Palace (NES) - Got the best car per AdamL's list.
Curious George (Xbox) - My niece had trouble with it (she's 4), but wanted to see the end, so I played through it for her. Surprisingly fun though!
Rock Band Track Pack 2 (X360) - Played through the career mode on Hard. I would do Expert, but I can't quite get the later songs.
Batman: Arkham Asylum (X360) - Finished the game on Hard.
Batman: Arkham City (X360) - Would've beat it on Hard if I didn't forget that the save I previously used was set on Easy and didn't realize it until late in the game. Definitely gonna go back at some point though.
Pocketbike Racer (X360) - Figured I should play through a bunch of quick shit games that have sat for years. Actually kind of fun, in a glitch-fest sort of way.
Dungeons & Dragons: Chronicles of Mystara (XBLA) - Beat it a crapload of times because I'm an achievement whore. Got 'em all though.
X-Men Arcade (XBLA) - Again, I beat it multiple times to clear out all the achievements. Still wondering why it sat on my hard drive unplayed for all these years though
February:
Pure Chess (XBO) - Another chess game. Not much to say, but it's definitely fun.
Gears of War (X360) - Beat it on co-op with a friend who wanted to stream it. I'll never stream a game with him again though...fucking douche
Mass Effect 3 (X360) - Actually, I beat the entire trilogy, but this was the only new completion I had from it.
Uno (XBLA) - Another full completion. Not bad, but grinding wins was a bit of a bore.
March:
Risk (PS1) - Played with two human opponents and rounded it out with Hard level AI.
Capcom's Gold Medal Challenge '92 (NES) - Finished on the top of the medal standings for the first time.
Call of Duty: Modern Warfare 3 (X360) - Finished the career on Veteran. Hate how they're pretty much ignoring campaign mode these days...
Genghis Khan (NES) - Went through the Mongol Conquest first, then graduated to World Conquest and took over Eurasia.
Nobunaga's Ambition (NES) - Much easier than I'd anticipated it to be. Ninjas are godly!
Shadowrun (X360) - Yeah, it's a multiplayer-only game, but I did manage to get the full achievement list, so I've marked it off.
Donkey Kong (2600) - Only two boards to beat, and I beat them.
Donkey Kong Jr. (2600) - This one has three boards, and I beat all of them.
Mouse Trap (2600) - One board that repeats endlessly.
Mr. Do! (2600) - Another game with a single board that repeats. Terrible port.
Carnival (2600) - One board that repeats...kind of a pattern with Atari games. But hey, a win is a win.
Solar Fox (2600) - Finished all 8 boards on Parent Mode. Gonna have to go back to do the real thing...20 boards on normal mode.
Wizard of Wor (2600) - Pretty much another infinite loop. I survived past the wave where the Wizard comes after you. Didn't manage to kill him though, so I'll be playing it again sometime in the future.
Video Chess (2600) - I was expecting this to be easy. Boy was I wrong! It's not flashy, but it's one of the toughest AIs I've played against!
Surround (2600) - Well, at least I don't have to play this crap again
Indy 500 (2600) - Played through all the solo modes. Not much else you can do when you only own one driving controller.
April:
Air-Sea Battle (2600) - Beat all solo modes, and boy were there a LOT! Still fun solo, but I'm pretty sure multiplayer is MUCH better.
Star Ship (2600) - This was a load of utter crap. Yeah, I beat all solo games, but only Lunar Lander mode was actually sorta fun.
Star Trek: Conquests (PS2) - Beat the campaign on normal as the Dominion. Short, but fun, I'll definitely be going back in the future!
May:
Streets of Rage 2 (XBLA) - I resorted to using a glitch to get the final achievement, but I don't care, it's done
Lego Star Wars: The Complete Saga (X360) - Beat it a while back, but the final achievement took a bit of grinding out.
The Lego Movie Video Game (X360) - Not as good as some of the Lego games I've played, but it's decent while it lasts. A fairly easy 1000g if anyone cares
Combat (2600) - I only count 2-player only games if I beat a friend who is trying to win, and I managed to do that, once, after a bunch of playing.
Frogs & Flies (2600) - Again, I managed to win against a friend who was trying to beat me, so I counted it.
X-Men: The Official Game (X360) - Not as bad as some of the reviews I read claimed. Another relatively easy 1000g.
June:
Golden Axe (XBLA) - Took a while to find someone to play an online game against, otherwise it's a very easy completion. Again, beat it ages ago, but I finally got around to knocking the achievements off.
The Secret of Monkey Island: Special Edition (XBLA) - This one hasn't been fully completed yet, as I still have a few achievements left, but since I beat one playthrough, and probably won't do the second for some time, I'm gonna list it.
Gemfire (NES) - I first played it years ago and thought of it as a good starting point for getting into Koei games. Now that I actually played it through, I gotta say it's far too easy for me to enjoy properly. Had it been one of my first experiences with Koei games, I think my opinion would be better, but man, is it boring! Use it as a gateway to the genre, otherwise skip it for something with more depth.
July:
Pinball Dreams (SNES) - Pretty sure this just goes forever, so I used the "beat the high score on every table" method to call it beaten.
Pinball Fantasies (SNES) - Same thing as above. Both games were okay, nothing special, but yeah, got the high scores on all tables so I'm calling it beat.
Aerobiz Supersonic (SNES) - Love me some Koei games, and this is one of the really good ones. Only drawback is that it's super short and super easy to beat. Kinda limits the replay value.
Mario's Time Machine (SNES) - Got the best ending. My god this was a slog. Just knocked it off so I never had to fire it up again. That said, it's still better than the NES version
August:
Civilization V (PC) - Finished it with (I believe) Boudicca, marathon game, small map. Love me some Civ!
Final Fantasy V Advance (GBA) - One of those games I bought when it came out and just never fired up. So, I fired it up, and kicked it's ass.
September:
Pure Chess (XBO) - A bit of a grind getting the Grandmaster achievement, but I managed to do it and put this game to bed. Love some chess, but even I have my limits. A great simulation though.
Goat Simulator (XBO) - I had more fun with this than I thought I would. Got all the achievements in the base game, and will buy the DLC as soon as I have money to afford it
Incredible Crash Dummies (NES) - I fired this up not expecting much. I ended up finding a hidden gem. It's got a few flaws, and is a wee bit easy (other than the end boss), but overall I really enjoyed this one!
Sunset Overdrive (XBO) - Finished the campaign. Still gunning for the 1000g base game (again, can't afford DLC at the moment), but I'm happy to finally get around to finishing the story!