My thoughts:
Halloween: A classic that still holds up. Jamie Lee Curtis makes the film for me, acting exactly how anyone would in her situation and bridging the catatonic Barbara from NOTLD and the survivalist action heroines of movies like Alien and A Nightmare on Elm Street. Fun fact: the house hwere Tommy Doyle lives in the movie a block over from where they shout Elm Street.
Halloween 2: A fantastic sequel! I love how Carpenter makes reference to the first movie then turns it in on it's head, like the pumpkin in the opening tearing open to reveal the skull. It's gorier and more action-oriented than the first, but I think it works in the movie's favor; also, setting it on the same night but moving the action to the hospital was inspired. If I were to watch one of the Halloween movies it would be the first, but the two are definitely part of a greater whole.
Halloween 3: Watching this movie on Halloween night is a tradition of mine; it just feels like Halloween! I love the story, I love masks, I love the scenes of kids trick or treating...it's just fantastic. I really think most of the movie's problems could be eliminated by just calling it "Halloween: Season of the Witch" and playing the main theme at the beginning. As it stands, though, I absolutely love Halloween 3.
Halloween 4: I liked this more the second time. It's another one that feels like Halloween, and the characters play off each other so well. Seeing the nostalgic costumes on Jamie's classmates is great, and the same goes for the scene in the drug store, not to mention the brilliant opening credits. The fault for me is that it doesn't really feel like a Hallowen (series) movie; it all feels kind of forced to me. That's why I'm hooked until about the climax, when the holiday trappings are cast aside, and that shouldn't be the case. The ending is clever, but I hated it when I first saw it.
Halloween 5: This was just really forgettable; I had to watch several trailers and read a few synopses to even remember what happened. It dropped the ideas set up by the end of Part 4 and just kind of limped along as a total mess, trying to do way too much at once. The problem was that it wasn't even a memorable mess.
Halloween 6: The problem with this movie was that it tried to give Halloween a mythos, like Elm Street or, to a lesser extent, Friday the 13th, and that was not a good fit for the series at all. I know the behind-the-scenes shenanigans, but it just doesn't forgive how much of a hot mess the movie is. It's kind of impressive that they made a movie where absolutely nothing works.
H20: It's better than 5 and 6, but that doesn't take much. Again, Jamie Lee makes the film, I love the Psycho references with Janet Leigh, but the story has some holes and there was too much use of jump scares. It was awfully triumphant to see Laurie get her revenge, though, and the false ending worked brilliantly. It's a pretty good film, but it only really works the first time around.
Resurrection: Good God. Like Part 6, it's just a nasty mess that ruins everything the previous movie has set up to end the series in favor of current slasher trends (in this case, found footage and self aware one-liners.)
Zombie 1: I actually really liked this movie for the most part, but it shouldn't have been called Halloween. It worked best as a deconstruction of the slasher film (the way Zombie tied in masks was brilliant), and if it were just that, spiced with references to Halloween and other genre films, it would have been great. A lot of people argue that Zombie "missed the point" by grounding Myers in a sort of reality, but if you want the Carpenter Myers, watch the Carpenter movie. Zombie couldn't beat it, and I think he knew that, so he looked at it from a different angle.
And I have yet to see Zombie's H2, though I really need to.