I forgot to mention Nicholas Roeg mainly because I can't believe no one has really mentioned him.  "Walkabout" was one the most gorgeous films!  For that alone he should be considered.  Also what about Coppola, I know that he's really awfull now, but "The Godfather" and "The Conversation" are masterworks.  I guess I judge a director on a sole film than on an entire body of work.  For instance David Gordon Green is a fantastic director, he made "George Washington" to prove it, yet he's not really considred great because he hasn't made as many films as Bunule or Kurosowa have.  Just some food for thought.