Most of the adaptations are really poor. There just isn't enough money on a tv budget to make the shows like the book. Take IT, loved the book, loved most of it until the end, the spider at the end ruined it for me. The Stand was the same. It was a good try, for such a large book, and like IT I loved it, until "The Hand of God" scene and it was terrible just bad CGI(and if you listen to the commentary on the Stand they weren't impressed with it either). His books are great, the characters are given life, you get to know them and love them and hate them. It is just so hard to put that on the screen.
Now for movies, IMO the more serious books make better movies. The Green Mile and the Shawshank Redemption, both were great movies very similar to the book. DreamCatcher was good, until the ending then changed it up at the end. Bigger budgets make better movies.
1408 was pretty good, for being from a short story and I am looking forward to the Mist and the Cell, so I guess that with better technology, maybe better movies.