I'll side with
Brandon on this one: "Citizen Kane" is, above all else, a director's movie. I went to see "Kane" in a movie theater with an actress who had never seen the movie before. She remarked afterwards: "I don't know why everyone thinks this is such a great movie. The acting was good, but it wasn't great." That's debatable (I think most of the acting is superb), but it misses the point.
Reviewers (starting, perhaps, with the influential Pauline Kael) praised the work more for the direction of Orson Welles and the cinematography of the incomparable Gregg Toland than for the acting. That was, in itself, a radical reorientation of film criticism, which had previously focused on the people on the screen rather than the people behind the camera. It's what they call in film school the "cult of the director," and that's very much the direction that film criticism takes today.
It's easy to see that, in 1941, people viewed movies very differently. "Kane" was nominated for nine Academy Awards but won only one: for best original screenplay. A review of the other
nominees that year shows a more traditional slate of "actor-driven" movies (only one other "director-auteur's" work was nominated that year: Alfred Hitchcock's "Suspicion" for best picture). When critics started paying more attention to the director than to the actors, however, the critical estimation of "Citizen Kane" rose considerably.