"The two films that have to be tied for first — and this is probably a hackneyed answer, but it is the way it is — are The Godfather, Part 1 and Citizen Kane. The Godfather is a perfect film. There is not one shot out of place, there’s not one performance that’s not the best thing that actor has ever done. There is not one thing about the film, visually, that’s not mind-bogglingly beautiful and elegant and astounding. And it shines a light perfectly on its subject matter.
I think that there’s a gravitas, because of the presence of Marlon Brando, in the first film, that elevates it [as opposed to The Godfather, Part 2]. Not to say that the second and third films aren’t great films also, but when you have something as historically important as the performance that Brando gives as Vito Corleone, as the kind of central fulcrum point, then it goes into a class all by itself. He achieved that three times in his career, as far as I’m concerned. One was On the Waterfront. One was A Streetcar Named Desire. And one was The Godfather. And although he was the prevailing genius of the day, on those three occasions he just elevated phenomenally brilliant films into a place that became uncategorizable. How did he do that? It’s so ethereal, and so indescribable, that you could try to analyze it from now until the end of time and you couldn’t begin to put your finger on it. That was an otherworldly gift, that he had.
Citizen Kane (1941, 100%) is tied for first with The Godfather. It just has to be, it’s such an amazing achievement."
Source