The 4th film was, after all, a bit of letdown, in that, up til now, each one was better than the last. This was the one directed by Mike Newell (the first Brit) and moves us into a more grown up world. We also finally meet the evil Lord Voldemort (Ralph Fiennes) in the reincarnated flesh.
But it really just didn't work for me as well as 2-3. Stripping away all the trappings of the wonder of being at a magical school should have worked, but it didn't, somehow. Maybe because there was no contrast. Maybe because showing sinister things is not as impactful as showing normal everyday happenings, with sinister overtones (this is what worked so well in Twin Peaks). The stakes weren't as high in #3, but the whole thing was so wonderfully packaged by Cuaron. It was a sheer visual delight, with details in every corner. Newell does away with all of that, and Harry's world just seems like he's in a normal fantasy world/alternate universe, as opposed to a secret world, hidden right under our noses.
The showdown with Voldemort was a letdown too. I don't know how the book portrays him, but here he's a screaming, wild madman, as opposed to some sort of evil genius.
I still enjoyed it. They dealt with the maturation of the characters well (including the raging hormones). But it wasn't as fun as #2 or #3.