I recently bought 2001: A Space Odyssey on DVD and just finished watching it again. I think the movie is still very impressive and beautiful, but what is most memorable and striking is the ending. A wordless presentation of images that does nothing to explain itself, but leaves the viewer entranced and weirded out, is a ballsy and awesome way to finish a film that was already strange and disorienting. 2001 was released in 1968, and now, in 2009, there still hasn't been a finale made that comes close to matching 2001's ending.
I think there was a chance though. The end of Watchmen (the comic book) is very strange, disturbing, and off-putting. The willingness to be so bold, graphic, violent, and flat-out weird really resonates and makes for a finale that's shocking. Can you imagine if the recent Watchmen film had ended with a giant psychic squid leaving NYC littered with corpses instead of the more clean and sterile Dr. Manhattan version? It would have made the film even more dense and alienating. Just an interesting thought.