Star Wars easily. If you saw it back in when it was released, it was a life changing event!
I was 5 when I saw Star Wars in the theater with my parents. I started crying when Han fired the first shot. My mother turned to me with a stern look and demanded that I stop crying because she said I was embarrassing her. I couldn't. She pulled down my pants in front of the entire theater and beat me with my father's belt. Life changing? You could say that. To this day I have not kissed a girl and I haven't seen a movie in a theater since.
You've gotta get everyone to agree on what defines quality science fiction.
I'd like to start off with "No Ethan Hawke".
We warn the reader in advance that the proof presented here depends on a clever but highly unmotivated trick. -- Howard Anton, "Elementary Linear Algebra"