E.T.: The Extra-Terrestrial (1982)
The reason Steven Spielberg's follow-up to Raiders has remained such an enduringly tear-jerking family classic (and earned him a second spot on this highly-contested list) is that, although it centres on a young boy befriending an alien, it's not really about science fiction. It's about the singular loneliness of childhood, and that's a theme that never gets old.