I'm not interested in Hollywood movies. That does not mean i dislike them at all. I just don't like today's films. That is why, my list consists of mostly European cinema.
Since the question asks "the best", it is hard to answer it but let me write the ones which are in my all times favorites and have special place in me.
1)Krzysztof Kieslowski (1941-1996)
The one that i like MOST. I have watched all of his films. I try to analyze and write essays about his cinema. I am thinking of preparing a super-detailed research paper.
Blue and
A Short Film About Love are my favorites.
2)Ingmar Bergman (1918-2007)
Bergman is special for me with Kieslowski.
Persona (1966),
Skammen (1968) and
Det Sjunde inseglet (1957) are my favorites.
Persona is different because i wasted my times on analyzing this film, reading Freud to explore this film further.
To sum up, if you really ask me to give my all times favorite film, i could say Persona.
I want to add that Hitchcock is the biggest directors in Hollywood. The most important reason to this that there isn't any director neither before nor after him, who can process his ability of high tension to the films. He is still beyond reach.
I have been preparing a research paper about "Hitchcock and His Blondes", recently.