Overall have to give the nod to "We were Soldiers Once" -- nothing else has done nearly as good a job at capturing what battle must feel like both in the field and for those left at home. Plus, Sam Elliot's Sgt role is priceless...
You beat me to it Simaril, "We Were Soldiers" is firmly 'Top 5" for me
We Were Soldiers
Blackhawk Down (my little brother fought in that battle, 'Chalk 2' Bravo Co, 3rd Rangers, their group dropped in on 1 corner of the Olympic Hotel to give support to the "D Boys" that had gone in to get Aidid's guys, and were closest to and first to arrive to secure the first Blackhawk that went down. He's not referenced by name in the movie but is many times in the book, as well as in the photos in the book. He lost a few really close friends that day, and couldn't make it through that entire movie the first few times he tried to watch it. According to him, you couldn't have made that movie any more realistic without actually killing people.)
Saving Private Ryan
Band of Brothers (call it a multi-part movie)
Enemy At The Gates
Das Boot
Bat 21
Still trying to find Battle of Britain, never seen it