Comparing LotR books and movies is like comparing the Pride and Prejudice book to the BBC miniseries starring Colin Firth. They're both wonderful, so much fun and so real, and they both manage to tell the same story with mostly the same words and events, but they each add their own elements. You can get the emotion of Darcy's first proposal (for example) in each version, but in the book you get the worded descriptions of what's going on, and in the miniseries you get the expressions that tell you the same things, just in a different way. (The newest movie version of Pride and Prejudice, though, is awfully inferior to the book - and the miniseries - in every way except for that gorgeous music and a couple of interesting shots.)
Anyway, I definitely think the Twilight movie is better than the book
It doesn't take a hundred pages (give or take) before anything happens other than Bella brushing her teeth and answering e-mails, and you can still laugh just as hard at it. And I don't think there was a single instance of the word "godlike," so that already makes the movie ten times better than the book 
Oh, and they cut out the amusingly horrendous, thinly veiled metaphors to Wuthering Heights and the Garden of Eden, so that's a plus....Does Death Note count? Mangas are books, aren't they?
The live-action movies were so much better than the original, even with all the stuff they had to cut out -_-Hmm, that's all that's coming to mind right now. Most of the really good adaptations I can think of are either adapted from something other than a book (like Prince of Persia: The Sands of Time), or are so different you can't even compare them (like I, Robot or I Am Legend).
EDIT: Oh yeah! I think the Inkheart movie was WAAAAY better than the book. The book kind of dragged in places, and Dustfinger got a much more satisfactory ending in the movie too.
:)
I recall a recent conversation around here, about how hard it is to get sarcasm across on the internet.
