Brothers in Arms: Road to Hill 30 is the pinnacle of FPS, squad based combat on the home console (in world war 2 form). If you're a Rainbow Six fan, or a Medal of Honor fan, this game meets you half way between the two; providing great story, challenge, and a fantastic squad interface system that will keep you playing all day long.
BiA takes place during the air drop on D-Day (before the beach storming at Normandy) and puts you right into the action, but not so much that you're scrambling to learn the controls. The guide you into being a leader; giving you one soldier at a time to learn how to work with, move, and keep alive. A great feature of the game is the field overview, which enables you to "pause" the game and allow for tactical decisions based on terrain and position.
The game is challenging, I've been playing it on normal and I've died my fair share of times. But unlike the defeat I feel in other games, I feel that, like any good soldier, I can get back on my feet and keep marching forward. The game even helps you along every-so-often by healing up your squad and reviving fallen men if you've died at the same spot a few too many times (this is a choice you have though, so if you're a glutton for pain you don't have to take them up on the offer).
The story keeps you going with trials and loss, if you've watched HBO's Band of Brothers, this is the game that will play out the parts. The graphics are quite good, and the sound is fantastic, even though it's mostly gunshots springing past your head. I haven't even tried online play yet, but the single player is good enough for this game to be as good as they get.