who is best Hollywood director?

Scorsese for "The Departed" - Absolutely brilliant film.

Tarrantino for both "Kill Bill" films, he's daring, experimental and a visionary.

Spielberg for his ability to perfectly gauge what Hollywood consumers want from a commercial Blockbuster. His films are a little bit too commercial nowadays, but he's definitely a great director nevertheless.

James Cameron for obvious reasons.

Christopher Nolan is well on his way to joining the directing elite after TDK and Inception.

John Ford for many movies

Orson Welles for Citizen Caine and Touch of Evil

I don't like James Cameron too much, he has plagiarized so many of his scripts. I counted three major plagiarizisms in Avatar alone.

James Cameron.

Orson Welles - what he did in "Citizen Kane" with the digicam angles had not been accomplished before and as such Welles inspired infinite directors who would keep on with at the same time with Scorsese, Spielberg and Nolan.

Scorcese.