The "Lord of the Rings" is indeed a classic masterpiece. However, the books have a singular flaw in them. Tolkien was a writer who spent more time on describing each and ever scene, right down to nearly describing every single tree, blade of grass, stone building, etc. What he lacked was making the reader really love the characters in the stories, along with a lack of actual conversations throughout the books. What the films did, even if they changed the story somewhat, was make you actually like, or even love, the characters: Samwise, Frodo, Aragorn, Gandalf, etc.
Character development was J.K. Rowling's strength in the Harry Potter series. You actually liked, loved, disliked, or even hated the characters. They key to writing great fantasy books, or any fiction book, is to see what the character sees, feel what the characters feel, and feel like you are them or at least living life along with them. A great plot for a story is important, but unless you can identify with the lead or important characters in the story, the story falls flat. At least that's my opinion.