The LA Times has a fun article on famous movie lines and those that wrote them.
There's a common debate about which should be given more weight when writing a screenplay - images or words. It's true that films are a visual medium. If it's words that are really important to you, be a novelist. On the flip side, people don't often go around saying, "Remember that smash cut in Planet of the Apes when the apes saw Taylor shaving? I really felt the significance of that moment." But think of how many times a day we quote movies, tv shows, stand up comics, even video games (some of my dearest memories of my first university were those lunches I went to and spent the entire time listening to my guy friends quote Red v. Blue to each other. "I'm from Iowa." Nobody cares!).
I was reading an interview, I think with Kevin Smith, where he said he wanted to write a movie that teenage boys everywhere would quote alongside their regular vernacular. Is there any other real pinnacle of success besides hanging out at a grocery store, the beach, Starbucks, and overhearing some stranger quote lines you wrote?
Really, you should be making all aspects of your story the best they can be. I think the crux of the debate is the question of which has the greatest power to communicate. Knowing which will serve your story best at every given moment, page, and line is a mark of a skilled writer.