From a technical perspective I cannot praise it enough. This film is a cut above most. It's absolutely brilliant. The use of contrast in lighting, leading for particular characters to appear as silhouettes while others in the scene remained the same, was brilliant. The extreme camera angles to express distant relationships... And the camera being literally sat down in the floor at some points, looking up at powerful characters, or vise versa, having the camera look down at those more diminutive. All around, simply genius Cinematography, and filmmaking in general. Citizen Kane should be required viewing for anyone perusing the art of film, or those captivated by the beauty and magic of film in general.
On the other hand, the story itself left a lot to be desired, in personal opinion. *Spoiler alert* What most likely ruined my viewing experience was being aware that "Rosebud" had been the sled, which took the joy of mystery out of the film. Had this not been known, perhaps the ending would have been seen as a surprisingly bittersweet conclusion. This man had everything; money, power... yet these things could never buy back that which was lost. Those blissful childhood days spent out in the snow with Rosebud. Ah, the sentimentality! It's an amazing film, an intricately told storyline. But I prefer things to be much more Capraesque. Charles Foster Kane was an ambitious, bold and charming young man who spoke for the people... and we slowly watch, in a biographical format, as he deteriorates into a needy, egotistical, cold old rich man forever alone. It does not even have the merit of being a tearjerker sort of sad, it's just plain depressing.
What is impressive and admired, is that Orson Welles, in his mid-twenties at the time, had total control over this picture; from Directing, Producing, Writing and Acting. Not to mention, this was his first feature film!
Other info about this picture can be found at IMDB, and Wikipedia.