Let me precede my list by saying that it's pretty messy. I'm sure that I'll end up adding/subtracting/shuffling a lot of the directors on the list before I make my official submission. Also, there are a LOT* of directors that I haven't seen any of, or enough of to list, so if my list has any glaring omissions, that's more than likely the reason. They're listed by name, and by the film which I feel is their greatest.
1.
Stanley Kubrick - 2001: A Space Odyssey
2.
Werner Herzog - Little Dieter Needs to Fly
3.
Steven Spielberg - Munich
4.
Quentin Tarantino - Kill Bill: Volume 1
5.
Hayao Miyazaki - Princess Mononoke
6.
Paul Thomas Anderson - Punch-Drunk Love
7.
Chan-wook Park - Lady Vengeance
8.
Martin Scorsese - Goodfellas
9.
Steven Soderbergh - Out of Sight
10.
Christopher Nolan - Memento
11.
Danny Boyle - 28 Days Later
12.
Joel & Ethan Coen - The Big Lebowski
13.
Spike Lee - 25th Hour
14.
Francis Ford Coppola - The Godfather
15.
Joon-ho Bong - Memories of Murder
16.
Spike Jonze - Adaptation
17.
Sergio Leone - The Good, the Bad, and the Ugly
18.
Terrence Malick - The New World
19.
Sidney Lumet - Dog Day Afternoon
20.
Clint Eastwood - Unforgiven
21.
Ang Lee - Crouching Tiger, Hidden Dragon
22.
Alfonso Cuaron - Children of Men
23.
Peter Jackson - The Lord of the Rings trilogy
24.
Darren Aronofsky - Requiem for a Dream
25.
Guillermo del Toro - Pan's Labyrinth
26.
Peter Weir - The Truman Show
27.
Akira Kurosawa - High and Low
28.
David Cronenberg - Eastern Promises
29.
David Fincher - Se7en
30.
Terry Gilliam - The Fisher King
31.
Gus Van Sant - Good Will Hunting
32.
George Lucas - Star Wars Episode IV: A New Hope
33.
Stephen Frears - The Queen
34.
Rob Reiner - This is Spinal Tap
35.
James Cameron - Terminator 2: Judgement Day
36.
David Lean - Lawrence of Arabia
37.
Errol Morris - The Thin Blue Line
38.
Richard Linklater - Before Sunset
39.
Woody Allen - Annie Hall
40.
Frank Darabont - The Shawshank Redemption
41.
Charlie Kaufman - Synecdoche, New York
42.
Paul Greengrass - United 93
43.
Cameron Crowe - Vanilla Sky
44.
Wong Kar-wai - Chungking Express
45.
Ridley Scott - Blade Runner
46.
Robert Zemeckis - Forrest Gump
47.
Michel Gondry - Eternal Sunshine of the Spotless Mind
48.
Rian Johnson - Brick
49.
Ramin Bahrani - Goodbye Solo
50.
Oliver Stone - Born on the Fourth of July
*Kenji Mizoguchi, Takeshi Kitano, Takashi Miike, John Woo, Johnnie To, Michael Haneke, Lars von Trier, Ingmar Bergman, Jacques Tati, Alfred Hitchcock, Billy Wilder, Orson Welles, Krzysztof Kieslowski, John Ford, Howard Hawks, Pedro Almodovar, Charles Chaplin, David Lynch, Jean-Luc Godard, Francois Truffaut, Jean Renoir, Federico Fellini, Buster Keaton, Milos Forman, Edward Yang, Agnes Varda, F.W. Murnau, Atom Egoyan, Jim Jarmusch, Andrei Tarkovsky, John Carpenter, Yimou Zhang, and Apichatpong Weerasethakul are just a few.