I find it hard to quantify the Harry Potter films. I enjoy them as a series, same as the books, but I can't really point to a particular one and say 'that was my most/least favourite'. I thought Half Blood Prince was a bit meh, but it was still serviceable.
I think Prisoner of Azkaban was where the series took off. After two fairly light-hearted kids adventures that were still experimenting with the concept, Prisoner of Azkaban had the kids starting to grow up, the story became darker and more complex and it established the background and set the stage for the big shift in Goblet of Fire. Plus it was a well-directed, well-acted film that set the tone for the rest of the series. Yeah, it wasn't as faithful to the books as the first two, but does that really matter? If you want a pitch-perfect recreation of the books, just read the books! I did, they're very good. But, if you want an adaptation that also makes for a good film in it's own right, you can do a lot worse than Prisoner of Azkaban.
I think Prisoner of Azkaban was where the series took off. After two fairly light-hearted kids adventures that were still experimenting with the concept, Prisoner of Azkaban had the kids starting to grow up, the story became darker and more complex and it established the background and set the stage for the big shift in Goblet of Fire. Plus it was a well-directed, well-acted film that set the tone for the rest of the series. Yeah, it wasn't as faithful to the books as the first two, but does that really matter? If you want a pitch-perfect recreation of the books, just read the books! I did, they're very good. But, if you want an adaptation that also makes for a good film in it's own right, you can do a lot worse than Prisoner of Azkaban.