Call of Duty

[Paradox]

I think it's a great game. It really portrays the environment of war in a realistic, chaotic way. Your fellow soldiers help you out a lot, as there is no way you could complete many missions by yourself. You go through three single-player campaigns (American, British, and Russian), then go into the multiplayer, which I think is pretty good too. My favorite SP mission is Stalingrad, the first Russian one.
I really recommend this, and if you look elsewhere on gaming sites, everyone rated this very highly.