"Citizen Kane" is possibly the most acclaimed film that I know of. It's been called the "greatest film of all time" by a lot of film critics, polls, magazines, etc.
The film is a chronicle of the life of Charles Foster Kane, a fictional character based off of William Randolph Hearst, a famous newspaper publisher. The film's structure is highly unconventional, in which Kane's life is revealed through interviews with various people who knew him well, making a majority of the film a series of flashbacks.
On both a technical and story level the film is quite influential. The story, itself, becomes far more bleak and dark than a lot of the films coming out at that time (at least in the US, that is), and it completely insults a very powerful figure (that being William Randolph Hearst) who was still alive at the time, and fought to get the film banned (just watch the documentary "The Battle Over Citizen Kane" and the drama "RKO 281", two films that are also quite great).
On a technical level, there's many extremely inventive techniques being developed here. There's one particularly interesting low angle shot that was made so low because Welles actually drilled a hole in the floor of the set. Other than that shot, you mine as well look at every single other shot or scene if you want to see some technical innovation. You could just analyze it frame by frame if you want to attempt to see all of its influential visuals, and you still may not have truly seen all of the detail. As Roger Ebert said on the commentary, "Citizen Kane" is actually a special effects picture. The main difference between this film's special effects and the special effects in a film like "Jurassic Park" (another greatly influential film) is that the special effects in this film are kind of hidden, but nonetheless powerful in their own right.
A lot of people may call it the #1 most important film of all time, but I have to disagree. While it certainly is one of the most important films of all time, one really needs to go back to the silent era to find all the TRULY most important films. Films like "A Trip to the Moon", "The Great Train Robbery", "The Birth of a Nation", and "Intolerance". Welles, himself, actually did say during his introduction of D.W. Griffith's classic "Intolerance" that that film deserves all the credit for a lot of modern cinema's techniques.
However, with all its technical innovations that have been talked on and on about time and time again, I've heard very little about how ENTERTAINING the film is. "Well that's because it isn't entertaining!" I can hear some guy who had overly high expectations (and gave the film 1 star with a lengthy review entitled "Disappointing") shout. Well, you're wrong, the film is quite entertaining! Sure, there's no action sequences, explosions, Adam Sandler doesn't play his twin sister, and Kevin James doesn't wackily fall down 420,000 times, but there IS true human emotion, iconic lines of dialogue, and a truly compelling imagery that ends with one of cinema's greatest twists! There was actually a time in my life in which I watched "Citizen Kane" nearly once a day because I enjoyed it so much! I genuinely watched it TWICE in one day just because of how much I enjoyed it, which is very rare with me.
If you're looking for the greatest film of all time, maybe you should lower your expectations a tad bit and just experience the film for what it is.
