Chinatown: What is it's place in film history?

Chinatown came out in 1974, decades after the genre it was portraying was popular. This example of neo-noir is a very, very good film. But after looking over AFI's 100 years 100 films I have to ask: how did it get ranked #21? Granted its a very compelling story and the characters are interesting and were acted extremely well. But is it really the 21st greatest film of all time?

What makes a great film? How do you rank works of art? By it's quality? It's contribution to the art community? Originality?

I feel that Chinatown is very good, but its not the kind of film that sticks with you. You don't keep thinking about it. It doesn't make you reevaluate things - your life - your perspectives - your humanity. In 1974 it might have brought a lot of cards to the art of film - but not to art in general. 

A film needs more than good direction, cinematography, acting, etc. At the Academy Awards it only won Best Screenplay - though it was nominated for many, many more. That's because it is a well rounded film. Polanski is a very gifted and ground-breaking director... he made a film that not only honored a genre of decades previous, but in doing so made one of the best of it's genre.

The themes of loneliness are there.

But when you have to rank the best 100 films of all time, I feel that it does other filmmakers injustice to place Chinatown at #21.

Can you really argue that the film is more significant than #30 Apocalypse Now, #33 One Flew Over the Cuckoo's Nest (which came out the year after), or even #52 Taxi Driver (2 years after). 

I'm not trying to be contrarian here. I'm not trying to just pick Chinatown out and rant about it. I'm just wondering if I am missing the larger message or if other films are being snubbed? The film is good, but how good? The film is compelling, but how compelling? The film is original, but how original? The film is significant, but how significant?

I'm not trying to be too negative, but I feel it is important to question critics that seemingly have a universal belief about a film.

Is there a difference between an art and a craft? I guess someone could argue that art is the significance of a craft.

How significant is Chinatown... in the grand scheme of things?