Broadly speaking, Hollywood makes war movies for two reasons that aren't profit-related (which we take as a given): to give the audience the slightest inkling of what actual battle is like (the closest most of us come is our biannual paintball game), and to commemorate the sacrifices our fighting men and women make, both on the battlefield and at home.
But every "best of" list of war movies inevitably includes a rotating group for the 20 or so everybody has already seen. I'd be a fool to argue against including Apocalypse Now or The Great Escape in any overall ranking, but there are thousands of war movies out there, many unknown to a wider audience.
So consider these an alternative to your annual AMC Midway - Saving Private Ryan - Platoon marathon.