Okay, I'm not a DD guy, but I'm a bit of a movie junkie and since MLB started the topic I reckon I can get away with posting...
So here be my top 20 (in no particular order)
Heaven Can Wait (1943)
Casablanca
Society
Citizen Kane
The Empire Strikes Back
12 Angry Men
M
Raging Bull
Annie Hall
Rushmore
The Jerk
Jaws
Fast Times at Ridgemont High
The Producers
The Philadelphia Story
His Girl Friday
Back to the Future
On the Waterfront
Raising Arizona
E.T.
I wanna give Ferris Bueller's Day Off, Clerks, Go, Class of 1984, Dr. Strangelove and Dog Day Afternoon honourable mentions as well. They all just missed out on the top 20.