This kind of comparison is less apples and oranges, in most cases, than raisins and watermelons, or, maybe closer, bluejays and bobcats--because inert black marks on paper are so qualitatively and experientially different from visual images in motion. Still, the question of whether one *enjoyed* the book or the movie more is perfectly sensible, so long as the one bears a reasonable narrative resemblance to the other. Of course, no one could ever have cinematically reproduced the sheer brilliance and pace of Daniel Menaker's novel "The Treatment," but the movie version did a pretty good job. (Seriously, I admired and appreciated many things about the film version of my own book but never felt very close to it. It was strange--almost an out-of-body experience--to see the movie, whose plot differed quite a bit from the book's. But most sophisticated readers/moviegoers forgive such liberties so long as the results are more worthy than cheesy.)
"Atonement": like Mr. Goodwood's friend above, I found it in some ways better than the book, especially in its chronological clarity. Should have won Best Picture over "No Country"--another truly brilliant adaptation but without a thought in its head. Well, maybe half a thought--about the endurance and inevitability of evil. "The Devil Wears Prada" also seemed to me very good, in its way, as a movie and a book. I think the best modern novel adaptation to screen was "The English Patient," which produced, for me, the same powerful insights and emotions in both media. And the recent film version of Alice Munro's story "Away from Her" was very strong--maybe "better" than the written version.
Other possible b-t-bs: "Thank you for Smoking," "The Diving Bell and the Butterfly," "The War of the Worlds" (Spielberg). No question far better than the book: "The Last of the Mohicans"--a seriously underrated movie. Surprisingly good and somewhat underrated: "Catch-22." Two best TV adaptations of novels ever: "The Glittering Prizes" (much better than the book) and "Brideshead Revisited"--remarkably close to the novel in feeling and subtlety.
Movies and books are always fairly safe topics of conversation, though too many disagreements about books and movies--and books-into-movies--can place a real strain on friendship, I've founf.