Elaborate. I know you are a smart man and probably have interesting things to say about why this is so.
Well...
J.R.R. Tolkien's Middle Earth
I knew next to nothing about The Lord of the Rings when I went to see The Fellowship of the Ring, but I found myself seeing the movie multiple times, reading the books, finding as much as I could about this Middle Earth. I was addicted. I loved the story. I love everything about the movies, and while the books are good, they are written pretty badly. So yeah, I am probably voting for this over the strength of the movies, rather than the strength of the books. Somehow, it influences all of my emotions... I feel happy when watching Pippin and Merry, I felt sad when the ring was destroyed, not because the ring had been destroyed, but because the story was finished... I would not see anymore of this story. I love it.
C.S. Lewis' Chronicles of Narnia
I read The Magician's Nephew and saw The Lion, the Witch and the Wardrobe. I thought the books were written badly and I couldn't get into the movie at all. So I don't like this.
Phillip Pullman's His Dark Materials Trilogy
I got halfway through the first book but it wasn't interesting me. I'll probably try the movie though.
Stephen King's The Dark Tower series
I've read the first two books and liked them a lot. I've got Book III waiting for me, but I'd rather wait until I've finished the series before I compare it.
Terry Pratchett's Discworld
I believe I tried one of his illustrated novels with all of the old warriors going up a mountain or something...
J.K. Rowling's Harry Potter series
I've read all of the books, but I stopped being a hardcore fan after Book 5. I just lost interest in most of the characters.
Eoin Colfer's Artemis Fowl
I believe there's only two or three people on UC who've read them, and I've read them all except for the latest one... the first three were pretty good, but I stopped caring after that. This series would be a lot better if it was just Artemis Fowl, Criminal Genius instead of mixing in all the fairy ****.
Other
I like the Star Wars movies, but don't care about the books.