The Battlefield Series is made by EA/DICE. In Battlefield, you can do just about whatever you want. Shoot artillery, snipe, tank, pilot, it is all something you can do in Battlefield games. All Battlefield games have many mods that will appeal to just about everybody. The multiplayer community is large and there are always servers.
Battlefield 1942 - The first Battlefield game focusing on World War 2. Has many famous battles, and has some of the war's key weapons and vehicles. It had some expansion packs that were never very popular. Popular mods include Desert Combat(Gulf War), Forgotten Hope(World War 2 Realism), and Eve of Destruction(Vietnam)
Battlefield Vietnam - The second Battlefield game, based on the Vietnam War. It isn't as popular as Battlefield 1942 and isn't as good. You will face punji sticks, bouncing betties, napalm boming runs, and much more. Popular mods include Point of Existence(Modern warfare) and Operation Peacekeeper(Kosovo)
Battlefield 2 - The third and possible final Battlefield game. It deals with modern warfare. It releases in June 2005.
There is Battlefield Modern Combat for PS2 but the only people that will buy it are those without a computer or those whos computer cannot run BF2.