Call of Duty 4 > MAG > Halo 3 > Gears 2 > Disgaea > Killzone 2 > Uncharted 2.

I only had a 360 at first, so I just played Halo and Gears for quite a while.

Counting Ps2, definitely one of the PES games.
Only current gen consoles, then Super Smash Bros. Brawl.

Cod4 easily put like 30 days on it lol

Probably Super Smash Bros Brawl. Over 100hrs. Haven't invested more than 50
I doubt I'll invest more time in any game again than Grand Theft Auto: San Andreas. Over 12,000hrs on that game.

Super Smash Brothers Brawl, mostly playing online with membesr of VGChartz.

This gen - that would be probably WoW (way over two thousand). But more recently, either GTA IV or MAG.

Resistance 2. I played this game every day for multiple hours a day for six months.

WoW with over 2k hours, then SSBB with around 250.

Soul Blade on the PS1.

Other games I know I spent an ungodly amount of time with are Final Fantasy VII (PS1, PSN), Tetris (Every console), Chrono Trigger (SNES), Street Fighter II (SNES), and Mario Kart (SNES).

EDIT:  This gen would have to be Lost Odyssey (360) or Mario Kart Wii (I can't remember which console).

More than likely Super Smash Bros. Brawl. I think I have a couple thousand hours logged into it.