I'm quoting from this article in the Nov/Dec 2013 Touchstone Magazine, in which Donald T. Williams explains how literature, while delighting us with its art, is more powerful than history or philosophy to nurture our moral vision, or to corrupt us with false images.Jackson apparently thinks the characters Tolkien gives us are too simply good to be fully believable to modern audiences, and so he feels obligated to "complicate" them, to give them internal conflicts other than the ones they actually have, in the hopes that we will better be able to relate to them.
With the help of quotes from Sir Philip Sidney, who wrote Apology for Poetry in the sixteenth century, he shows how "Tolkien was very consciously and deliberately following the literary tradition that flows down to us from Sidney through Dr. Johnson and C. S. Lewis."
Peter Jackson the filmmaker seems to be flowing in a different stream. But he is an artist, and of course will impart his own soul to his work. I wouldn't expect him to give us The Rings, because that has already been done, and he is not J.R.R. Tolkien. But it is unfortunate that he has changed things to the degree and in the directions he has. Williams points out specific ways in which the characters who inspired us in the books disappoint us in the movies, and makes these general remarks:
Read the whole article here.