I will strongly defend John Cassavetes as nearly excellent filmmaker who could have become even one of the greats if the system would not oppress him all his life.
Jean-Luc Godard (since another reviewer used him as an example) is somewhat overrated as well. While he directed several excellent films early on, some of his middle age and, especially, later films are quite sub par. One should not choose a single filmmaker and put him/her as a "benchmark". Film-making is so complex and dynamic process and this is why it is so much fun to have so many different film styles, film presentations, film "languages", film cultures.
Every time when someone authoritatively tries to single-out the "benchmark" freedom suffers.
If one watched first couple of Fassbinder films (for example) at the time of release and dismissed these (with 1-2 "stars") and should that one had enough influence to oppress (like in former socialist countries), Fassbinder would has never been able to realize himself as one of the greats later on.
While Cassavetes is not one of handful of the greats he came close enough with some of his films and deserves at least 4 stars using current Amazon rating system, which, by the way, is quite poorly designed as rating should have been from 1 to 10.