I have 12 games completed with 1167/1912 achievements at 23,170gs.
The games I've completed are Dead Space, Dead Space 2, Fallout 3, Fez, Limbo, Mass Effect 2, Mass Effect 3, The Orange Box, Portal 2, Scott Pilgrim VS The World, Terminator Salvation, and The Walking Dead.
I was working on Just Cause 2, Left 4 Dead, Left 4 Dead 2, Mass Effect, and Skyrim a few months back but I got a new computer and haven't gotten back into the Xbox yet. I need like one more achievement in Braid but I'm too lazy to get it lol
Terminator Salvation (one of my 100%s) was the absolute worst game I've ever played.
I had the most fun with the Orange Box. The Aperture Science achievement from Portal and the "treasure hunt" achievements in Half-Life 2 and its episodes (finding the hidden supplies and killing every last grub) had me wanting to smash my television, but other then that they were pretty great. My favorite achievement from the game and probably out of all the games I own is "Little Rocket Man". I want to do it again.
I like going for 100%s - I feel that I've experienced everything the game has to offer that way. I like the immersion. I've also been working on Twilight Princess and Skyward Sword, but there aren't statistics for that, so whatever.