Although your question was about WWII movies, I would add that "Sgt. York" was the best war movie of all time. "All Quiet on the Western Front" was also good.
If we're going to start listing movies that focused just on American servicemen, I think we would be remiss in not including,
The Deer Hunter.
Just the finale of that movie was worth sitting through the other three hours; plus, it was Christopher Walken's breakout role!
I know the war was actually peripheral to the main plot, which really focuses on the maturation of a group of young men living in Pittsburgh, but I still think it was one of the best "war" movies of the 20th Century.
All great choices.