2001: A Space Odyssey
2001: A Space Odyssey is more than just a film, it is considered by many to be an Odyssey of Spatial Dimensions. It is notable for a) Being very good b) Making very little sense and c) Blowing your mind so that you don't have any idea if the pertinent questions about humanity, evolution, war and technological advancement are answered or even, in some cases, asked. Some of the problems posed are answered by the sequel 2010, which disappointed many people by only being a very decent science-fiction thriller. (For avoidance of all doubt, 2012 is not the threequel.)
Mark Kermode often says "Stanley Kubrick went from the beginning of civilization to the birth of a new species in just over two hours" when discussing films that are very long and not very good (eg Transformers: Dark Of The Moon or the Pirates Of The Caribbean series ("it took eight hours to get from Point A to Point A")).
He has however acknowledged that he has a problem with the fact that, rather than work as an allegory as most science fiction does (eg District 9 is not about aliens, it's about racism; Starship Troopers is not about bugs, it's about fascism), 2001 was written by someone absolutely fascinated by how human beings might really, actually find alien life.