This is a list of whom I believe are or have been the best directors, and what is, in my opinion, their best film. The list is NOT in order - there's no rank. In my opinion, a great director needs to have outstanding films to their name, and also needs to have a catalogue of films showing consistently good directing. Some will disagree, but that's the great thing about having different opinions.
The idea with the list is that, if you've seen the film, you click on both the film AND the director; and of course, the opposite if you haven't. Cheers!