Movie board put I feel the OB will have better opinions on the best military movie. I'm going with black hawk down, worst by far is hurt locker.
Blackhawk Down is up there - I'm a softie for the classics:
The Longest Day
The Sands of Iwo Jima
A Bridge Too Far
Full Metal Jacket
And one not a lot of people remember, but it was the template for Full Metal Jacket - The Boys from Company C
There are great made for television stuff, too: The Pacific
Band of Brothers
As far as newer (at least to me) - Eastwood's films Flags of Our Fathers
and Letters from Iwo Jima
form an excellent double feature.