I think Alien 3 is a good movie and doesn't deserve the hate it gets. I do agree that Alien and Aliens were better, but I think Alien 3 is a good movie with a fittingly bleak atmosphere that lends to the horror. Although I do agree that the Assembly Cut is far superior to the theatrical cut.
I mean, I can understand people hating on Alien 3 when it came out in the early 1990's because it was a dark and almost Gothic form of horror film and was a massive change of pace from the action-packed awesome that is Aliens. Plus, as stated earlier, Alien and Aliens were cinematic masterpieces, so Alien 3 had a tough act to follow.
But after the cinematic abortions of Alien: Resurrection and the two Alien vs. Predator movies, I'm surprised people are still salty about Alien 3 (even James Cameron spergs about how much he hates the third film, though I understand his hate for the fourth film), although I have heard that Alien 3 is much more popular in the United Kingdom and Europe than it is here in the United States.
Either way, I'm just glad that Alien is making a comeback indirectly via Prometheus (which was an okay film, but not as good as the first three Alien films) and now directly through Alien: Covenant. Let's hope that Covenant can fully revive the franchise after Alien: Resurrection and AVP killed it.