My WWII game of choice is Battlefield 1942. The core game is great, and there are also several good mods - there is one (name forgotten) that is much more realistic than the unashamedly arcadey basic game, where it rarely takes more than two shots to kill someone and all the vehicles have realistic armament (as opposed to fighters with 15 bombs). There is also Desert Combat, which usually has more servers running it than the un-modded game - it combines maps based on modern desert conflicts (mostly Desert Storm stuff, but I think they are adding some others) with the maps from the original game, so you can have some rather surreal battles (Coalition vs. Iraq on Omaha Beach). The only other mod I have played is Eve of Destruction, which is set in Vietnam and is very well done. They even changed the weapon recoil model around to make it more realistic.
Anyway, if you get BF1942 you essentially get several great historical team-based FPSs with a lot of vehicular action, at least on the PC. I’ve heard about some console versions of BF1942, but I haven’t kept up, and with consoles you don’t get mods.