For me it's not a matter of how strictly they follow the source material. I love Kubrick's The Shining though it differs greatly from King's. Coversely, I am one of a very small group of people who didn't care for the movie version of The Green Mile which didn't differ from the book in any perceptible way.

In my analytical model it's not a matter of how closely an adaptation mirrors the source material but how effectively it uses the crux of the source material. What I'm saying is that I judge them in part on their own merits, and in part on their effectiveness as adaptations. I think that's perfectly fair.