Allright if pressed these are my Top 5 all time:
1) L'Aventurra - No one else mentioning Antonioni in this post is a crime. His knowledge of architecture and use of landscape to represent character's inner lives is something rarely seen or matched in cinema. Not to mention all of his breathtaking long shots. This is the most obvious choice but any of that trio or "The Passenger" would have fit here too.

2) In the Mood For Love - WKW and Christoper Doyle have made some of the most beautiful movies I've ever seen. But this is the crown jewel. Perfect from start to finish visually.

3) Last Tango In Paris - Bertolucci is a master. "The Conformist" is his best film and "La Luna" may be more beautiful (although 5x as disturbing) but not only does the mood of the story find representation in the camerawork there is also a strong homage to Francis Bacon and his paintings that is consistent throughout if you look for it. I could watch this movie 20 times and never be sick of looking at it.

4) Days of Heaven - Malick is a genius and this is the film that really proves it. Not everyone can do so much with so little. His poetic pauses and atmospheric surround shots all add to the story. I think you could argue that "New World" is more magnificent but the natural lighting both in and outside in this film is spectacular.

5) Barry Lyndon - I had to pick a Kubrick and this is probably it. Unbelievably detailed set pieces and everything else done to perfection.

Honorable Mention: The Proposition - Saw this at Sundance this year and was blown away. Shot on location in the Australian outback. Breathtaking natural shots under extreme circumstances. The actors told us that several times they had to stop shooting b/c it was so hot the film was melting in the camera. People that love westerns with great photography should not miss this film.

BTW