some films you have to watch twice, usually because the ending changes the perspective so much that you have to see the film over again to understand it from that new perspective. A great film for that would be the Cabinet of Dr. Caligary
Other films are so rich with so many layers that you must watch them multiple times to fully understand and appreciate them. Well Tartovsky's films are definately like this, I recomend Egoyan's Exotica. The film becomes more beautiful with every viewing. I think I've watched it seven times so far, and I will be watching it again soon.