Groundbreaking, influential, or simply memorable installments in the science fiction genre, for better or for worse. Movies which I think all fans of the genre would enjoy in one way or another, and movies which I think ought to be taken as a given part of the conversation when talking about sci-fi. This is not meant to be a list of personal favorites, although it will doubtlessly be inflected with my taste and preferences.
What am I missing? What belongs here that maybe I haven't even seen? What do I have here that doesn't belong? What would be in your essential sci-fi canon?