I was recently asked to comment on the question, "What is best and/or worst book-to-movie spec fic translation project ever?" Here is my response to the "best" part of the question:
I can think of three approaches to this question. The first and simplest is to identify the best (or worst) film that happens to be based on a work that we define as "spec fic," which I take to refer to the sf/fantasy/horror continuum. Consulting my top 100 movies of all time list, I see that that happens to be The Shining. The second, more nuanced, approach is to identify the film that adds to and/or reimagines something inherent in the source material, but elevates or transcends the source material. Using this "value-added" approach, the answer is, again, The Shining, though, look--poor blood-soaked Carrie is right behind. The third, and most nerdly, approach would be an appeal to faithfulness to the source material. So... Lord of the Rings? Watchmen? Since this method points in the direction of Zach Snyder, I prefer not to pursue it.