As the title states the game/games you most enjoyed completing, had fun doing it or actually felt thats what gaming is all about.
We all have different opinions on games thats why there are so many different titles some really really awful, some you play for a few cheap gamerscore. But every now and then a game arrives that you keeps going back, and love playing hour after hour. For me the game would have to include multiplayer to have made me go back again and again.
Here are mine. My opinion only because i loved every single cheevo
Borderlands 1500g - One of my favourite games ever! co-op
Halo 3 1750g - Halo need i say anymore love multiplayer, some hate it!
Graw 2 1000g - Probably best multiplayer community, everybody talked!!!
Remember just games you loved not grinded for 30 hours checkpoint killing, unless you love that lol...
There's been a few but Rainbow Six Vegas 2 was memorable, a good bunch of guys (one or two from this site) came together to make what could have been a boring grind something fun instead
Most recently, Splinter Cell Conviction, excellent single player and even better as a co-op if you've got a good mate to help or at the very least one that can press X when appropriate (*cough Blain cough*)
Next up is Resident Evil, still not done but again when a certain few of us come together it's fun, provided I can remember to use A to run
I liked Tomb Raider especially Legend because the collectibles actually got you things that were useful, like the Soul Reaver from the Legacy of Kain series. I really like platformers. I'd also put Assassin's Creed in there (minus, of course, the stupid flag collection).
For Nostalgia purposes, I really enjoyed going through the classic Banjo Kazooie games.
And lastly I'd put Silent Hill: Homecoming because I enjoy that series.