I saw this question raised elsewhere and I was curious to get the screened community's input on the matter. What makes an adaptation good? Is it faithfulness to the source material? Surely it has to be somewhat faithful to be an adaptation at all but if it's exactly the same whats the point? Does it focus on exploring the theme of the original or focus on the details? I think of something like RED that takes the characters and concept, but completely shifts the tone. Alone it's a fun action comedy that I thoroughly enjoyed but does that make it a good adaptation? From what I can tell anyone who have read the original absolutely loathes the movie (maybe that can be chalked up to temperamental comic book fans).
For me above all what makes a film adaptation good is that it has to stand on its own. First and foremost I love movies, sure I like to read as well but mostly that is non-fiction stuff so I'll generally not have read something before the movie comes out. The movie has to be able to tell a cohesive story, not assume you know things from the book, and don't lean to heavily on the 'wink and nod'. An example of it done wrong (for me) is the last 2 Harry Potter movies, they dwell on things that hold no meaning to those who have only seen the films and pass quickly things that should be expanded. Why do I care about these characters who die? They've had a (maybe) a half hour of screen time in the last 6 movies! Sorry, I'm starting to derail.