Battlefield 2 would be my first choice, followed by Call of Duty 2.
Although, the problem with online gaming these days are the cheats. I have never worked out the point in cheating. The gaming community have tried to stop cheating with PunkBuster, but many cheats are not detected for example on BF2 you have Clear View,Tank Jacket, AAbot, Clipper, Radar001 and others that get past the PunkBuster anti cheat software.
In the end, it's down to the individual to enjoy gaming and don't take it too seriously.
BullDog(UK)