Film schools can teach you technique, but they can't always teach you taste. For that, you need to watch films — not just any films, but the ones that demonstrate what cinema can achieve at its highest level.
This list represents the essential viewing for anyone serious about understanding cinema. Each film on this list does something that no other film has done before or since — they expand the possibilities of the medium.
Watch them in any order. Watch them multiple times. Watch them with the commentary tracks. These are films that reward attention.