I'm firm in Fellowship being my favorite. It was the first, the most fun, and simply a joy. I'm also just as firm in my belief that Two Towers is the best film. The last 20 minutes or so, from when the Ents march on Saruman, to the last ride of Rohan, and Samwise's epic speech is about as perfect as cinema gets to me. Brilliant.
I never could properly sort out the Potter books from the movies. The first two are simple reads, and they are simplistic films. HBP is a sloppy read, and it's a sloppy film. Mostly I just watched them with an eye on seeing the novels come to life, and while I have major quibbles, they all mostly hit the broad strokes (sometimes too broad but whatever). Goblet of Fire is the quintessential Potter book to me, and I don't think Rowling ever outdid it as far as plotting and story. The film hits bumps, but I really enjoyed it in the main. The graveyard scene was goosebumpy,