Discounting books based on films obviously... I think Shawshank is better as a film and I haven't read it but just read a review of Atonement (absolutely brilliant film) which said it was better than the book.
If you haven't read the book, how can you form the opinion that the film was better? I've both read the story, and seen the film many times. In my opinion, the film is good, and it adheres closely to the storyline of the book, but the book is still better. You should read it for yourself, and then form your own opinion.
The only movie that I can think of that I consider better better than the book is JAWS
fredthe3rd...in response to sundrop "i haven't formed an opinion...i made that perfectly clear"
but the first line of your initial post states emphatically...and i quote : " i think shawshank is better as a film...and ihaven't read it..."
i once conversed, online, with a dude regularly used to review (diss, actually) albums/songs without ever listening to them....
but, to answer the Q...the only time i ever read a book and liked the movie more was the original 'planet of the apes' movie as opposed to pierre boulles novel...which i liked, but not nearly a much as the serling written, heston starring classic