I can't believe I didn't even post a placeholder here...but anyway, I'll get to it. I only track new completions, 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.
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
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.
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 - 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.
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 - Beat the campaign on normal as the Dominion. Short, but fun, I'll definitely be going back in the future!