Starcraft 1/2 - SC1 was the best RTS for a long time, slow plodding RTS just don't do it for me, SC was the only one that had real intensity.
Supreme Commander - the original, took the intensity of SC but applied it to long term strategy as opposed to mad micro. A grand epic game without the long intervals of nothing that most strategy games of this type have.
Quake 2 Rocket Arena 2 - played this online nearly every day for 3-4 years.
Baldurs gate 2 - the best story based RPG I've played
System Shock 2 - coop mode was awesome.
Hidden and Dangerous - the original. Flawed interface, buggy, but one of the best coop games I've ever played.
Quakeworld - I was never any good at this, but I won't deny that's the best 1v1 or FFA FPS ever made.
World of Warcraft - Gets a lot of hate because it consumed too many people for too long, and when you're doing the same instance 50 times waiting for a helmet to drop.. you got to ask yourself whether this game is worth the time invested. That being said, it defined a genre, I've recently gotten back into it and am pleased with the new end-game. If you know to avoid the monotony of going for a perfect gear-score, this game is still fun.
EVE Online - The only MMO that has a real player driven environment. A pain in the ass to get into, requires an attention span most gamers simply do not have, but it provides something no other game has come close to providing.
Master of Orion 2 - My favourite TBS.
Civilisation 1 - yes, the original, the one that I sank the most amount of time into. Probably my first "binge" game.
Diablo1/2. Nuff said.
I think that's more than 10. Ah well
