Yep, Jaws was a book. The Godfather was also a book, and, from what I've heard, not a particularly good one at that.
Just a couple of things about Prisoner of Azkaban that I forgot to mention: Sirius and Wormtail, I thought, were perfectly cast. Unfortunately, the scene set in the Shrieking Shack at the end of the movie displayed the Big Reveal in the most obtuse, confusing manner possible, and I doubt that non-book readers understood it very well.
Onto the second half of the series (warning, another mega-post incoming):
Order of the Phoenix...I thought it was solid enough, but there were plenty of flaws along the way. As I said before, the running time was way too short, meaning that a ton of the book got left out. The reveal of Snape's worst memory was done in an extremely rushed manner, and it just made Harry look like a jerk for directly attacking Snape, instead of having him snoop around and get himself into trouble as in the book. Something about the "newspaper montages" felt wrong, as if to say, "well, we'd like to show you all this stuff that's happening, but we didn't feel the need to shoot a few quick scenes that would've worked just as well." And for what a huge deal Harry's kiss with Cho was, his breaking up with her is only alluded to in a single scene without much dialogue.
As for the good stuff...Umbridge was just as despicable onscreen as she was on the page, and Helena Bonham-Carter and Ralph Fiennes make the most of their very scant screentime. The big character death at the end was true to the book, where it happened suddenly and with little warning. And to cap it all off, we have the Dumbledore vs. Voldemort battle, the biggest one-on-one fight scene in the series up until the last movie. Pretty good stuff.
Half-Blood Prince, I felt, was a step in the right direction in some ways and a step backward in others. On the good side, the comedic moments worked very well, especially considering that the second half of the series is almost completely lacking in humor otherwise. They managed to find a child actor that could actually pull off being a creepy young Tom Riddle, and the teenage Riddle actor was very sinister as well. Slughorn looks like he's at least twice as tall as he is in the book, but as usual, the actor was well-cast for the part. Tom Felton really hit his stride here with the conflicted character he played. And, like the rest of the death scenes, this one stayed true to the book, where the character death was seen first, but it didn't really strike you until Harry returns to the body a few minutes later, and then it hits you like a brick, even though you knew it was coming.
As for the not-so-good stuff, the action scenes here left much to be desired. The Burrow getting attacked is a pretty good example of what not to do in a story with slow pacing: splicing in an action scene for the express purpose of making sure the people in the audience are still awake, especially if there are no consequences afterward. Seriously. The Burrow is just fine in the next movie. There were no repercussions for what happened. The Inferi in the cave provided a pretty good jump-scare, but when you actually see them, you realize that, individually, each Inferi looks like the lovechild of Gollum and a Holocaust victim. It's very odd. Greyback, one of the most vicious bad guys in the books, totally gets the shaft here, and non-book fans will only know him as "that really ugly guy who never says anything." The reveal of the half-blood prince's identity will leave non-book fans going "so what?" since it doesn't make any difference in the context of the movie. Finally, there was a big fight scene in the book at the end, and almost no fighting at all in the film, besides a couple of spells being reflected back at the user, and Bellatrix damaging property via arson like usual. Hagrid's hut is on fire? No worries; like the Burrow, it'll be just fine later.
Deathly Hallows Part 1 was an odd case. Hogwarts doesn't appear at all, and neither does Dumbledore in any capacity; Voldemort's snake gets more screen time than he does; the big three spend almost the entire movie camping; and respected actor Bill Nighy shows up to play a character who is only in two scenes and then gets bumped off off-screen immediately afterwards. The bad stuff was mostly the pacing of the movie. While this one has more action than most of the movies, it still gets bogged down by the overly oppressive atmosphere and the endless wandering that takes up much of the middle act. It doesn't help that while they wander, they wear the Horcrux around their necks and get moodier and moodier, bringing to mind some obvious parallels to the One Ring. I really have no idea what happens to Wormtail in the movie. It's pretty clear that he's dead in the book, but in the movie? I have no idea. Also, it suffers from one of the big complaints about the two Breaking Dawn movies: too little happens in Part 1, while too much happens in Part 2. This is the case here, where only one Horcrux ends up getting destroyed, making this probably the one movie that you can skip without missing out on much.
Fortunately, there are good aspects as well. The Tale of the Three Brothers was done brilliantly, portrayed with some really trippy animation. Yaxley went from being just another random Death Eater in the book to a full-fledged British gangster in the movie, while Scabior underwent the same process, going from a nobody to a stylish pedophile Goth. Truly a terrifying combination. Meanwhile, the snake attack in Godric's Hollow may go down as the scariest scene in all of the Potter films. Bellatrix is truly nasty here, and the big death scene at the end had a lot of people in tears, thinking to themselves: "This is so depressing! And I didn't even like that character!"
Lastly, Deathly Hallows Part 2. Oh man, was this movie awesome. You could just tell by the enormous amount of memes that it spawned literally overnight that this one hit the ball out of the park. Probably the biggest movie of 2011, one of the highest-grossing movies ever made, and an extremely high rating on Rotten Tomatoes. Talk about ending the series with a bang. It still had some problems, sure. The opening act was kind of slow, and the epilogue scene was about as well-received on film as it was on text (not very). A lot of stuff had to happen off-screen, which is really too bad because I would've liked to have seen some of the characters go down fighting, rather than having the heroes come across their bodies later. And Voldemort giggling like a child--and then hugging Draco a couple minutes later--could be some of the most unintentionally amusing moments in the series. (I think the Draco hug was supposed to be awkward, though).
On the other hand...the Battle of Hogwarts. All of it. I don't think I've seen something like that since Return of the King. Masses of Death Eaters shooting spells like archers shooting arrows at the force field surrounding the castle. That weird bridge you would see every so often getting destroyed to take down a huge amount of baddies at once. Revisiting the Chamber of Secrets. Luna addressing Harry by his full name to get his attention. Ron and Hermione's kiss. The statues coming to life. The Fiendfyre absolutely incinerating the Room of Requirement. Voldemort looking like he's just taken a blow to the gut every time a Horcrux is lost. The spiders that we haven't seen since the second movie coming out to play. The biggest Patronus ever, cast by Dumbledore's formerly bitter and hopeless brother. Everything Neville does--everything. Molly being a badass at the end. The crazy fight scene between Harry and Voldemort, which more than makes up for the extremely anticlimactic showdown in the book. The death of Voldemort's snake, followed seconds later by himself. This could be one of the most satisfying death throes of any movie villain I've ever seen. I'm only hoping something similar happens to Shadrack in TSL. And last but not least, Snape's backstory. The scene that made adults all around the world cry like babies. And I think I've said enough on that front.
All in all, I think the movies had a solid run. Some are definitely better than others, but they hold up in the long run. I don't know that I'll ever bother watching the first two again, but I pretty much liked them all from Goblet onward, to some degree or another. And it's telling that I, someone who is very cynical about the film industry in general, actually liked a movie series that ran for eight movies. EIGHT. FREAKING. MOVIES. Most movie series go straight down the crapper after the initial film, and this one kept my interest for all of them. And it's even more incredible that the final film, which is usually the worst in most movie series, ended up being one of the best films that I had seen in years. Kudos, cast and crew. Kudos.
And with that, the longest post ever comes to a close.