The plot is epic, but pretty straightforward: a kid's small town family comes into a lot of money and his Mom sends him off to the city to grow up proper against the objections of his Dad who believes in a firmer hand close to home.
The kid grows into a man and decides to spend his money running a newspaper for fun. It loses money, but he's got enough. Then he figures out how to make a profit--by inventing stories! Business starts booming and soon he starts to think he can invent anything. He collects companies, artwork and property and even people until he owns as much as any one man ever could--except that the people eventually leave him, scandals eventually ruin him and all the stuff he owns becomes so much clutter as he dies alone in his mansion with only a nurse to hear his last words.
So what's so great about that? Is that the best plot anyone ever came up with? Well, like with most things it's not the content so much as how it's treated. Despite the fact that it was made at a major film studio it was still only made by a first-time director who had merely worked in radio and theater before that. So, basically it was little more than an independent film, requiring clever solutions where money was lacking. The director of photography was a film veteran as were the screenwriter and film editor, but the star, co-writer, co-producer and director, Orson Welles, was an inexperienced, brash and bullheaded young man with something to prove.
So what, though, right? Why does it still top critic's lists after all these years? Can no one come up with a better story or direct a film any better than what some newbie did in the 1940s?
Well, see, the thing about it is: "Citizen Kane" isn't just good at one or two things like clever dialog or nice lighting. No, it's good at pretty much everything. More than just being innovative, well-made and grandiose it's also completely capable of being minutely dissected.
Sure, the story is told in flashbacks before that became common, it has a mystery that leads to a twist ending that actually ties the entire movie together without seeming tacked-on and even the sets themselves transform simple sound stages into expansive worlds of looming proportions. But it's the fact that you can also take it apart and study individual scenes--even individual still frames!--on the basis of character positioning, story, film composition, lighting, camera angle, costuming, make-up, special effects (yes, special effects), editing, set design, sound design and even acting style that makes it so great. And it only deepens the further you go! You simply can't over analyze it.
Orson Welles was known for making spectacular stage and radio play productions (even convincing radio listeners that Martians had landed in New Jersey, the stunt that actually got him the job as a film director in the first place) and he makes the film as magnificent as all his talents and youthful exuberance could muster. He pushed everyone to do his best work. New camera techniques were developed, theatrical staging was employed, radio sound effects were utilized--heck, even shadow puppets were used! All in the effort to make the best movie anyone had ever made and many believe he did it so successfully that it may never be topped!
Whether or not that remains true one can only guess at, but more than all the film school homework this motion picture engenders is the fact that it's actually quite a good flick. It's funny, it's romantic, it's intimate, it's ambitious, it's mysterious, it's dramatic, it's even abstract in places and bigger than life, and, besides all that, it's cool-looking (yes, even in black and white). It's so chock-full of good stuff that it's hard to believe it's only two hours long.
What's more, the film didn't start out as a huge hit or anything, mostly due to the fact that the main character was actually (more than loosely) based on a current leader of industry at the time (famed newspaper publisher William Randolph Hearst) who tried to get the film destroyed before it was ever released. It took a summit of all the Hollywood film studio heads of the day to defeat him and his attempts to bury it and ruin them all.
Even so, Hollywood insiders felt that Welles was too vainglorious (even for them) and they tried to snub him and end his career, but the film survived and it wasn't until years later, until after all the political maneuvering had died down and the film could be appreciated on its own merits that it showed itself to be more than a mere timely gimmick.
And that's a little about what's so great about it. See it for yourself and don't worry about getting a headache from trying to see all the greatness because the best part about a good movie is that you probably won't even notice!