I agree with most of them, the movies aren't that bad, but obviously they can't be as deep and have as much back story as the books.
It's the case with almost any popular adaptation, don't go a theatre and expect somebody reading the book from the beginning to the end, and expect sometimes very, very shitty adaptations.
I'm looking at you Eragon

This is what happen to every books that get a movie, cartoon or anime, ever.