How about the granddaddy of all scifi films, Le Voyage dans la lune by Georges Melies? Yeah, it looks primitive now, but it is generally considered the first science fiction movie. Watching the age of science fiction evolve from this to les Vampires, The Lost World, King Kong, The Wizard of Oz, Forbidden Planet, 2001, Star Wars, An American Werewolf in London, Innerspace, Terminator 2, Twister, The Matrix, The Lord of the Rings trilogy and Avatar is quite remarkable, and will be interesting to watch it evolve further in our life times (true 3D interactive?).