Alien 3 is by far the worst of the series. How can you enjoy Alien/Aliens when you know it's all pointless? That all Ripley's efforts are in vain? AvP and AvP;R are not great films by any stretch of the imagination but enjoyable enough in themselves and don't spoil your enjoyment of what's gone before, they're pretty much standalone. I remember watching the Alien series at a cinema which was great, people jumped to their feet and clapped at Ripley's immortal 'Get away from her you bitch line". When it came to Alien 3 however about 3/4s of the audience walked out to pass 2 hours at the Forbidden Planet. About 2/3rds came back for Alien 4 I think Sigourney made the right choice in not doing the prequal although it could have worked, she, Cal and her crew arrive at the derelict to finish the bugs once and for all and watch some form of recording showing the origin story.