My favorite movie of 2015 falls into this same category. The Pearl Button, a documentary by Chilean master Patricio Guzman, melded the history of Pinochet's genocide with the eradication of Patagonia's seafaring indigenous peoples. It is the middle film of a projected trilogy (his earlier Nostalgia for the Light was just as fascinating), and I can't wait for Guzman's concluding film.
Ultimately, films are like nutrition and exercise. Eat a healthy meal or take a long hike, and you'll grow stronger. Watch the latest Marvel craptacular, you'll get an ephemeral sugar buzz. Watch a Pure Flix movie, you'll clog your cerebral arteries with its narrowing worldview and its bias-confirming prejudices. But choose 12 Years a Slave, Love Is Strange, or Nostalgia for the Light, and you'll be nourished by good art, not to mention strengthened to do good and be good in our great world.