This may have been done before, don't know. But...
For me, Platoon. Although I didn't serve in Vietnam, I did served (1968-72) during the war, in the Air Force. There's many things
in the movie that strikes a chord with me. Some of the terms they used were the same ones we used in the barracks & other
places. Referring to the US as "the world", boo koo as lots of something and so on. The partying scene in the bunker was very much like
I experienced. You had the "juicers" in one area, and the "pot heads" in other parts of the barracks. Thus, the music played
in each place was decidedly different too. That scene where those guys partied to Smokey Robinson & the Miracles, I was
one of those guys. Several of my high school classmates went over & fought. One buddy in my art class in hs was in Bravo
company. All these years later, I look at that in an entirely different light.
American Sniper from a few years ago runs a good second place.