I'd have to say Star Wars: A New Hope, for the same reasons that David mentioned. Except I was 13 at the time - perhaps an even better age for it.
Others in the top five:
Dead Poet's Society
Room with a View
Casablanca
Kelly's Heroes
While we're on the topic of bests...
Best Radio Show: Hitchhiker's Guide to the Galaxy (BBC)
Best Book: Dune
Best TV series: Star Trek TNG