Steven Spielberg’s 1987 “Empire of the Sun” http://www.imdb.com/title/tt0092965/?ref_=nv_sr_1
was the first movie to show me the power of the background in storytelling. The acting certainly occupies the foreground, yet it is the musical score, location, extras and emotional tension that makes the story complete. I watched it enough times to justify owning it and the accompanying soundtrack.
My grown-up answer since 1987 would be “The English Patient” for all the same reasons listed above.