Maybe 'cause Hollywood does make a lot of really stupid movies (and more ppl are exposed to them than say, trashy novels) and if you don't get the subtext, it can be hard to tell the difference.
Sturgeon's Law, folks--90% percent of works in any medium, in any genre, are crap. Which ones make the top 10% can be highly subjective.
Oh, and to those who come out of Avatar hating humans, remember that the Na'vi are (somewhat idealized) primordial humans. Go far back enough and your ancestors lived in small groups where everyone's family, got their food directly from the land, and connected with the land and animals. There's still people like that today, and guess what, they're getting raped, massacred, and forced off their sacred lands so the place can be clearcut, stripmined, and otherwise destroyed. As always, their conquerors think that might makes right.
http://www.survivalinternational.org/