Well I'll actually give you an order.
1. 8 1/2 
2. Weekend
3. To Live
4. Napoleon 
5. La Dolce Vita
6. Landscape in the Mist
7. Andrzej Wajda's War Trilogy (A Generation, Kanal, Ashes and Diamonds
8. Color of Pomegranates
9. The Grand Illusion
10. The Man With a Movie Camera
11. The Conformist (Good luck finding it)
12. The Seventh Seal
13. Jules and Jim
14. The Bicycle Thief
15. Solaris
16. Last Tango in Paris
17. The Exterminating Angel
18. Ran
19. The Passion of Joan of Arc
20. Wild Strawberries 
I'll stop there because you asked for twenty.