HBO's "Band of Brothers" series was incredible. Should be on your list. Agree with "Boys in Company C" and "Full Metal Jacket" "Saving Private Ryan" although not a true story was fairly accurate in depicting what WWII combat must have been like. As far as realistically depicting a true story the old black and white "Sgt York" is still today a pretty darn good movie.
Oh, man! How could I have overlooked
Sergeant York?
Speaking of Gary Cooper, it's not quite a war flick, but since we're being flexible, The Friendly Persuasion is a great movie.