NarniaExpert, you are obviously welcome to your own opinions, but the somewhat astonish me. To call Caspian "a faithful adaptation" of the story is to display extreme ignorance of the plot line of the book. You're welcome to think what you wish of the quality of the film as a film, and to enjoy the plot of the film as a tale in its own right, but it is folly to pretend that the film was faithful to the book either in spirit or particulars.
If you've never talked to a Narnia fan in real life who "hated" the film, then you've never talked to someone like myself, who has been a fan of the books for over 40 years. Even I would not use the term "hated" to describe my reaction; "disappointed" would be closer. But regardless of how you personally received the film, the hard fact is that many, many true fans of the books were so alienated by what was done to the story of Prince Caspian that they became suspicious of following films. Though I have no empirical data to support my guesses, I nonetheless speculate that part of the reason Dawn Treader is doing poorly at the box office is that a certain percentage of lovers of the books walked out of Caspian saying, "Never again" - and meant it.
Also, I disagree with your assessment of frequenters of the NarniaFans forum. I'd categorize them as more fans of the movies than of the books, though there is an admixture of both.