Easily, easily the best film of this series. This isn’t just a great “Harry Potter” film, it’s a legitimately great fantasy film in its own right. Director Alfonso Cuarón is of a much higher standard than the other directors that helmed the series, and it really, really shows.
A lot more is changed between the book and film here, and I think that’s fantastic. The atmosphere and general strengths of the book (the character relationships, the themes, the style and tone) are built upon in unique ways, as the slavish devotion to the text that the previous two films is exhibited is cast aside. The cinematography between this film and the first two (let alone the later instalments directed by David Yates) is night and day; it’s so much more creative and expressive here.
The worldbuilding, a strength of J. K. Rowling’s, is expanded upon and adapted here in such a magical way. Additions like the shrunken heads are delightful, and the way Cuarón adapts elements like the monstrous dementors is so compelling. And Hogwarts actually feels like a real place! Rather than be so confined to sets, the characters are outdoors plenty of times, and the establishment of a proper geography for Hogwarts and surrounding areas was kept by the later directors of the series.
The new cast additions are great. Michael Gambon as Dumbledore lacks some of the magic of Richard Harris, but largely does a good job, especially in the quirkier aspects of the character. Emma Thompson, David Thewlis, and Gary Oldman especially, all embody their characters wonderfully, and really add to the strengths of the film.
The plot is more interesting than that of the first two films, definitely, but lacks a lot of the cohesiveness and structure, a byproduct of adapting the novel more loosely. There are some honest-to-God plot holes here, much as I hate the term, and the series would continue to make less and less sense to those who hadn’t read the books, as certain elements (such as the identities of the Mauraders in this film) are simply never explained to the film audiences.
Nonetheless, the film is such a rousing success in all other ways, that I don’t hold that too much against it. I give it three and a half bottles of butterbeer, and a time turner.