The Matrix
Gandhi
Silence of the Lambs
District 9
Rocketman
I've seen every single one at least three times, and that matters because I don't rewatch a movie unless I think I'll get something more out of it by watching it a second time--and I've seen a ton of damn good movies.
I can't exactly pinpoint what makes a great movie in my opinion, but here is a start, which I think is true of all of my top 5: it has to say something fundamental or profound about human nature, and perhaps make me self-reflect in some meaningful way.