Jack Nicholson's only role as a detective in a "modern" noir film that doesn't try to be anything else other than a modern take of a noir film. It is because of this, that the 1970's sensibilities that are just a natural result of being a film of this era, along with it's "twisted" twist ending, that Chinatown comes off as being a work more layered & "edgy" than a standard mystery film. Which ends up giving this movie a much more distinctual feel that surpasses the genre in which it respectfully tries to remain faithful to.
And when you think about it, aren't those the type of qualities that usually make a classic film a classic?
9/10