Well, frankly, I still don't get it. It's a good film, sure, but the greatest film ever? Why? What makes it so damn good?
Yes, the cinematography is unquestionably excellent. Gregg Toland produces some magnificently iconic shots, and his use of deep staging is superb. There were some great technical innovations, true, but technical innovation does not make a great film, it makes a cleverly created one.
A lovely atmospheric shot - but is it any better than what Universal were doing in their monster movies around the same time?
Welles's acting is powerful, but not, in my opinion, a truly awesome performance compared to many others - Mitchum in Night of the Hunter, Neeson in Schindler's List, Brando in Godfather, Hurt in Elephant Man, or Depp in quite a lot of things. The rest of the cast are fine, but that's it. The music is OK, but lacks the punch of scores like Scott of the Antarctic, The Sea Hawk, Battle of Britain, or even Star Wars, Pirates of the Caribbean or Gladiator. The story doesn't really resonate with me - Hearst was a foreign media mogul of times past, who's even less relevant to me than Robert Maxwell. And yes, the script has some good lines, but I think it's often confusing and loses pace.
I'd say that Kane is an extraordinarily well-shot film, with an interesting structure, but I still don't see why so many people think it's the greatest film of all time. Wikipedia's page on films considered the greatest ever makes interesting reading - it's as if great film-making stopped in the 1950s, according to critics and directors. I love old movies, but I don't feel that movie-making reached its peak in its first half century. Do we really think that no film made in the last 67 years was as good as the 25-year old Welles's 1941 debut piece?
I don't know what I'd consider the greatest film ever, but it sure as hell ain't Kane. What do you think?