If you have not see this films, I will not take you seriously in an argument about films. I am the first to admit that I have yet to watch several cultural touchstone films, such as The Lord of the Rings Trilogy and Jaws, but these are the films that you must see or I will not respect your opinion when you tell me I didn't "understand" Social Network.
1) Terence Malick's Days of Heaven (1978)
2) Alejandro Gonzalez Inarritu's Amores Perros (2000)
3) John Ford's The Searchers (1956)
4) David Lynch's Blue Velvet (1986)
5) Fritz Lang's Metropolis (1927)
6) Jean-Luc Godards' Contempt (1963)
7) David Fincher's Zodiac (2007)