Final answer:
The 1986 Best Picture Oscar winner featuring Johnny Depp and Forest Whitaker in supporting roles is 'Platoon', a gritty Vietnam War film that departs from earlier war movie portrayals of glory and heroism.
Step-by-step explanation:
The Best Picture Oscar winner from 1986 in which Johnny Depp and Forest Whitaker have supporting roles is Platoon. This film is set during the Vietnam War and is known for its intense portrayal of the war's effect on soldiers, contrasting greatly with the patriotic stories seen in many World War II films. Unlike the earlier war films that featured renowned actors like John Wayne inspiring America's troops, Platoon presents a much darker and realistic view of war. Movies like Platoon serve as a stark reminder that the realities of war are far from the often glorious depictions seen in earlier cinematic portrayals.