If this gen:

1. The Lord of the Rings: The Battle for Middle-earth II
2. Supreme Commander
3. Left 4 Dead 2

If all time:

1. Age of Mythology
2. The Lord of the Rings: The Battle for Middle-earth II
3. Supreme Commander

1. Mass Effect 2
2. Medieval: Total War 2
3. Dragon Age: Origins

1. Warcraft 3
2. Starcraft
3. Deus ex

1. StarCraft
2. Half-Life
3. Diablo 2

1. Warcraft 3
2. World of Warcraft
3. Dungeon Keeper 2

1- Starcraft/ Starcraft broodwar(Can I count these as one game since broodwar is an expansion?)

2- Oblivion

3- Command and Conquer: Red Alert 2

1- Diablo 2
2- Starcraft
3- Baldur's Gate 2: Shadow of Amn

All time:

1. Deus Ex
2. Half-Life 2
3. Age of Empires

This gen (odd... all RPGs):

1. Mass Effect 2
2. Elder Scrolls 4: Oblivion
3. Dragon Age: Origins

1- Civ 2(complete)
2- Civ 4(complete)
3- Age of Empires 2(complete)

1.) Team Fortress 2
2.) Quake(+Mods)
3.) Battlefield Bad Company 2(Believe it or not, this is actually among the best shooters on PC.)

All because of MP, not counting SP in any form since I've gamed total on PC online way longer than playing by myself. I love WRPGs and many other games as well but I've always spent way more time fragging in general.

ps: I'm not counting MMOs.... way different imo....