I thought the remake of The Time Machine was better than the book, but the book was like 100 pages. However, I thought the book, "The Island of Dr. Moreau" was adequate at 100 pages. It was much more descriptive than Time Machine, and I think the movie and book were fairly equal.
Being both a film buff and a voracious reader I will say that IMHO, the film exceeding the book in artistic value almost never occurs. However, the one great exception to this rule happens to be one of the finest American movies ever made:
THE GODFATHER
The movie is a masterpiece, the book is simply pulp fiction.
I think the movie is better when the book was boring or slow but the movie was fixed up to be more exciting. Do yo notice how some books come out after the movie?