Greatest American novel is a subject that exists along side such topics YouTube topics who the fastest guitarist is , or the fan boy delights of slinging invective at each in the course of ruminating on the image of Superman v The Hulk. The fun in all that is that it inspires everyone to put on their Expert Pants and invent conditions, causes and criteria for their favorite --guitarist, Super Hero, novel--and use them as bludgeons against a legion of other equally engorged enthusiasts who, in turn, have their individual favorite and wield rhetoric devices no less bludgeoning.
Even Norman Mailer, who was honest enough to admit that he actually wanted to write something called the Great American Novel admitted , after decades of brilliant books, that such a thing, a single entity,does not and cannot exist. The American Experience, or any historically collected National Experience, is too complex and changing too fast for one set of qualifications to set permanently. The greatest American novel, I think, will only be decided, finally ,when we are extinct and someone else , something else assumes the job of figuring out who we were, what we did, and what of that is worth a damn thing.