Runaway Jury. Actually most of John Grisham's books that were turned to movies did the books justice.
This won't make any sense, but I also like the Bourne series. The books and the movies have nothing in common except the main character's name, and a general concept (trained assassin looses his memory), but I thought they were both great as 2 separate stories.
The Cross series by James Patterson turned into some pretty good movies with Morgan Freeman (Kiss the Girls, Along came a spider, I think there was another one).
Tom Clancy's Jack Ryan series had one or two decent movies. I liked Patriot Games.