I just recently watched all the HP movies for the first time; having never read the books. I thought they were just fine; they can't all be the best movie ever.
they are the best books ever though. well, maybe not, but they are really damn good. and the movies are average at best. maybe they are fine in a vacuum, but not if you compare them to the books. and, yknow, the books aren't exactly easy to make movies off, but not that hard either. they could be a lot better.
To do the HP books justice in a movie theater, you'd have to do a treatment like Lord of the Rings... except there's about twice as much material in the HP books. The first movie did a pretty good job... by taking the very shortest book and making a movie with a 2.5 hour runtime. Most of the other HP movies had comparable runtimes, but the books got longer and longer, so the movies in general got worse. They managed to do better by splitting Book 7 into two movies... except that Rowling really could have skipped over the 100 pages of camping and doing nothing in the beginning of that book.
that would be a fair point, except the movies are wasing large amounts of time on pointless scenes, and with that they're at least somewhat responsible for the lack of time on the scenes that matter. the best example for this is the scene where harry tries to get to the dragon without flying in the fourth movie.
that scene isn't even in the book! why do that. I know, the answer is they thought it was an action scene that sells.
and the sport, however you spell it in english, is such a waste of time. the sport itself is stupid, over half of all players don't matter in most matches, it's something rowling designed in the first book and couldn't fix later, and it's also hard to do it well in the movies. so why not skip it? that would buy time for other stuff.
the fifth movie was the only one that did skip it I think. I also thought that was the best one.
and for the last book, well splitting it into 2 movies would be a good decision, but if you grind through 80% of the book in the first movie, the usefulness flies out the window. instead of doing the book justice, they got a large amount of time to flesh out the battle and invent even more scenes that aren't even in the books for the second movie. that's not doing it right.
