Medal of Honor: European Assault.
Probably the best war game I've played on PS2. As far as the controls and the sharpness of the game goes, nothing touches it.
Call of Duty 2 pissed me off because I was looking forward to it before it was released. The game play was wack - you can't crouch and peak around a corner (which is essential in first person shooter games), the game was set so that once you reach a certain part of the level the game would advance. This is gay because it doesn't really matter about the objectives or if you killed the enemy or not, you can just run until the level proceeds.
Killzone (I think?) was pretty tight too. More of a futuristic and fun to play type game, wheras MOH is more realistic and tactical.