It changes all the time, but at the moment my top ten are:

1. The Seven Samurai (Akira Kurosawa, 1954)
2. A Clockwork Orange (Stanley Kubrick, 1971)
3. The Searchers (John Ford, 1956)
4. Aguirre, The Wrath of God (Werner Herzog, 1972)
5. The Seventh Seal (Ingmar Bergman, 1957)
6. The General (Buster Keaton, 1927)
7. City Lights (Charles Chaplin, 1931)
8. Das Boot (Wolfgang Petersen, 1981)
9. The Last Picture Show (Peter Bogdanovich, 1971)
10. The Good, The Bad, and The Ugly (Sergio Leone, 1966)

saving private ryan is the best in my opinion