Shawshank Redemption, The Running Man, A Time to Kill, and The Warriors are some that I thought were better than the books, in the case of A Time to Kill it was the performances of the actors that made it better than the book.
The Running Man, IIRC, was a Stephen King short story. Relatively straightforward. The movie hammed it up to the nth degree, which made it a fun guilty pleasure.
Didn't read Shawshank, another King work.
Seeing the trend, I'll add The Shining to my list. Kubrick took the skeleton of the book but cut the fat and added a lot of muscle. The Shining remains a top 3 horror movie for me and borderline top 20 overall.
