Call of Duty (CoD) is another WW2 game, similar to Day of Defeat (DoD), but this time involving Russians as well as Yanks and English against the Germans. What I like about this game is the attention to detail in the game, the way the shots impact with bodies, terrain, etc, it gives it a Band of Brothers look to it.
The idea is to play as part of a team, as it will require team work to achieve some objectives on the single player level. You start as a rookie US paratrooper going through training (this is to give you training in the weapons, movement, etc). From there you move to D Day and then to helping the British, where upon you become a British paratrooper for a few missions. From there you become a Russian at Stalingrad (aka Enemy at the Gates style!) and fight your way to Berlin using a sniper rifle and tank!
The multi player has a variety of maps to play on and there are the usual Death Match and Team Death Match, there is also Search and Destroy, Behind Enemy Lines and Head Quarters. All in all the multi player makes a damn good game and you will be surprised at how well complete strangers band together to work as a unit to achieve the objective of the map.