Here are the online games I have
Return to Castle Wolfenstein: Good in it's day, but not many people play it now.
Wolfenstein: Enemy Territory - spin-off from Return to Castle Wolfenstein and is free.
Battlefield 2 - Bit laggy with the big maps and vehicles but fun.
PES5 - Sometimes fun, annoying if your opponent has lag.
Halo - Okay, don't play it often.
Call of Duty 2 - Haven't played it in awhile but it's good.
Counter Strike: Source - You have it anyway.
Day of Defeat: Source - I think you have this aswell.
Unreal Tournament 2004 - Don't play it much but have been meaning to play it.
Doom 3 - Another one I haven't played much that I should do.
Quake 4 - Another I should probably play more.
I probably play Wolfenstein: Enemy Territory the most because you have objectives, rather than "Capture the flag" and there is skill aswell with users able to tweak there settings to get better FPS, better shooting and even improve trickjumping.