Okay, I am well aware I am behind the game, and I've never read the books, but I have seen all six Harry Potter movies. As a guy who's started writing speculative fiction and has a Young Adult book planned, I felt a responsibility to be familiar with the most popular fantasy series released in the past decade. One disclaimer though: because I have yet to read any of the books, I cannot speak to the author's work but I will talk about the filmmakers.
It should be noted that Chris Columbus is one of my favorite directors and writers. His films like "Home Alone" and "Mrs. Doubtfire" have entertained me over and over again. And although I have no idea what was cut from the book, the first two films really worked for me. They were tightly written and engaging, getting you into the story quickly and moving things along.
Alfonso Cuarón's "Prisoner of Azkaban" was weaker but still engaging and entertaining. It was at the next film, "Goblet Of Fire," where things started to go downhill. I don't know if Mike Newell has issues with editing or if he just tried to do it himself, but "Goblet" was too long and took way too long to get going. It was at least 45 minutes into the movie before I got interested in what was going on, and that is way too long. The only reason I didn't just skip it was a feeling I needed to watch each film to get the others after that. But I shut off the DVD this time with none of the satisfaction the earlier films had provided.
"Order Of The Phoenix" and "Half Blood Prince" also left me wishing they'd been done by Columbus instead of someone else. They just needed a steadier touch by a filmmaker like Columbus or even Cuarón who knows how to make mainstream blockbusters. The lack of such direction was obvious and, ultimately, unsatisfying. Which is too bad, because people are so passionate about the books and even the movies. They deserved better.
I will also say that length was an issue, particularly for later films. My friends who read the books tell me they cut a lot, but I don't think they cut enough. Some of the beginning stuff was so long and dragged out that the real hook of the story takes forever to occur, and while that may work in novels, it is not good filmmaking. Surely even JK Rawlings must understand that they are different mediums, and, as a result, many things must be handled differently. Unfortunately, these films suffered from the same syndrome as many Hollywood releases these days, filmmakers unable to separate from their own babies and vision and make a film for audiences and not themselves. It is a wonder so many kids could sit through these. I truly wonder at what point their attention spans gave out. I know mine gave out a number of times, and I broke up most of the later films into sectional viewings as a result.
Those who love the films and books will likely disagree with me, and perhaps some filmmakers will as well, but as a person who went to film school and made television and films for a while, I can tell you my perspective is much more subjective than it was during that period. Audiences want hooky, entertaining films that move along, make them laugh, make them feel, and then end with a good satisfaction. For me, the Harry Potter films could have done this better.
I hope the books do when I read them. For what it's worth...