Some interesting points raised in this article:

1. First, to the above point, yes, I think this is the best directed film of the franchise.

2. However, I think that with the exception of the final film, the screenplays were too faithful to the books and failed to translate literature into great cinema the way Peter Jackson did with The Lord of the Rings. I like the films, but I think they are now considered classics through nostalgia, rather than great cinematic merit (although this film is very well directed, as you point out).

3. I strongly urge you to read the novels (you imply that you have not). They are vastly superior to the films. JK Rowling is a fantastic storyteller (I'm also very fond of her current Strike detective series) and this one in particular (Prisoner of Azkaban) is a masterpiece of fiction. I found the book a lot more moving than the film.