For the most part, I have a lot of issues with each of the Harry Potter films except one and I know I'm in the minority on this: The Deathly Hallows Part 1. It helps that The Deathly Hallows is my favorite book of the series (another unpopular opinion) and I loved the camping scenes, both in the book and in the film (yet unpopular opinion). I thought the film was exciting, emotional, and a great adaption of that portion of the book. It's just a damn shame Part 2 fell flat on its face (and not just because they fucked up the Neville confrontation).
I liked all of them except for the horrible first two, but Azkaban is my favorite, I liked the visual changes very much.
The Deathly Hallows, Part 1. I absolutely love the darkness, despair and hopelessness that the characters experience in this film. I love how lost they feel as they keep traveling across the countryside, unsure of what to do or where they are going. It's so moody and atmospheric. I remember reading the book and feeling this way, and the film completely captured it.
My favorite was Azkaban. I liked the visuals.Too bad they did not call back the Azkaban director for another harry potter movie.
PoA, for the reasons cited above, and because it hit the sweet spot where there wasn't so much material that they had to significantly gut subplots that I cared about (GoF was worst-hit by this given that it's supposed to be a whodunit). Also Lupin is one of my favorite characters, and this is, regrettably, the only film where he's given things to do that make him feel like more than an extended cameo. Also, time travel.
Azkaban was the first movie to brutally gut important storylines, which really pissed me off at the time, but I'm used to it now. They don't even explain that the Marauder's Map was made by James, Sirius, Lupin, and Pettigrew! That's kind of important! Looking back on it, how much better would the first two movies have been if they'd be cut down to shorter run times? The first one especially.
1. Deathly Hallows 1 2. Deathly Hallows 2 3. Prisoner of Azkaban 4. The Half-Blood Prince 5. Goblet of Fire . . . . . 6. Chamber of Secrets 7. Philosopher's Stone
Azkaban. But DH1 is up there. The less said about Phoenix and Goblet the better. I guess the order would be: 1. PoA 2. DH1 3. SS (PS) 4. HBP 5. DH2 then ... 6. CoS 7. GoF 8. OotP
I've been watching them for the first time over the last eight months or so and have one left to go. So far I think films four and six are the best, with the former appealing largely due to the performances of Gleeson and Tennant. Haven't read the books, so I'm judging these movies for what they are and not for how well they capture the best of the source material.
I thought Tennant's performance was an unfortunate digression from the novel personally. But then, I thought most of GoF was an unfortunate digression from the novel. That one in particular left me wishing I'd seen the movie before I read the book.
The GoF left out the most important scene in the book: the reforming of the OotP at Harry's bedside. Seriously, that's what the whole story is building toward - the idea of setting aside allegiances and prejudices for a higher purpose culminates in Snape accepting Dumbledore's orders to rejoin the Death Eaters as a double agent. It's one of the most critical scenes in the whole saga - and it's completely left out of the films.