Action
Terminator I/II/III
Die Hard
The French Connection
Ronin
The Seven Samurai

Drama
A Clockwork Orange
Cinema Paradiso
Taxi Driver
Blue Velvet
The Godfather I/II

Comedy
A Fish Called Wanda
Monty Python and the Holy Grail
The Life of Brian

Ack...I cannot think of any other legendary comedy flicks off of my head now.

Romance
Plein Soleil
When Harry Met Sally
Annie Hall
Before Sunrise
Kissing Jessica Stein

Others
Rashomon
Lost in Translation
Manhattan
2001: A Space Odyssey
Casablanca
Schindler's List
Saving Private Ryan
The Three Colors Trilogy
Lawrence of Arabia
Ben-Hur