Here are SOME (and I do mean only some) of the reasons that Alien 3 is one of the worst films ever made.
In the very first scene there is a facehugger egg. Where the hell did that come from? Surely not from the queen as her egg sack was torn off and shot with grenades. Second we CLEARLY see the facehugger jump onto Newt's cryotube yet Ripley is the one that was impregnated? Huh? How did this happen? Now the facehugger cuts itself (it's pretty unclear in the release cut how this happens but in the Workprint we see it cut itself on broken glass from Newt's cryotube) and bleeds acid and starts a fire. Next we don't see the computer even TRY to put the fire out it, just decides to eject the humans into deep space rather than put out a fire. That's pretty bad fire protocols.
Now they crash on Fury 161. We now see the facehugger attack and impregnate a dog, the same facehugger that we later find out inpregnated Ripley. As both of the first films, all of the comics, books and technical manuals state, 1 facehugger impregnates 1 host and dies, and here all of a sudden this one gets the dog AND Ripley. I bet the producers thought no one would notice.
We are told that NO hair can be left on a body here because of lice, right? Well unless I am mistaken dogs have hair (fur is basicly the same) yet this does not seem to be a problem.
The Aliens have no eyes yet throughout the film we see POV shots. It may have looked cool but it totally messes with what we know of the Aliens.
It took the Sulaco, 19 days in Aliens to get from Gateway Station to LV-426 yet it takes Bishop II less than 2 days to get to Fury 161 (which is only 4 days out from LV-426), they must have made some damn good advances in flight technology in the 4 days Ripley, Newt, Hicks and Bishop were in space (I get this figure from the "official" Aliens sourcebook).
Also letting the convicts stay on Fury 161 makes no sense. It would cost MILLIONS of dollars a year to run the "Prison" that was on Fury 161. We have already seen that the Company has NO concern for human life what-so-ever and cares only about money, so it is just moronic to think they would spend that much money to let CONVICTED KILLERS stay there just because they found god. By their own admission the station is not used for any mining or any other real function anymore. They also state they have tons of flashlights but NO batteries. Then in the next scene ALL of the convicts are using working lashlights BUT they never got batteries for them.
In the workprint there are more subplots and it is edited to make a (somewhat) coherent film as well as actually giving the characters a bit of personality. I think Fincher is a great director but an overbearing studio and awful script make it next to impossible to get a good film out of this piece of shit. The studio cut the film to hell then blamed Fincher when it failed. Typical.