I wouldn't call it a masterpiece either. There's a helluva lot of good in Alien 3. Thomson and Fincher's style (I certainly emulated Thomson a lot in college), Goldenthal's score is my favourite, Weaver is fantastic in that film, so are most of the cast who get put in front of the camera to speak, creature design, etc, that film just doesn't stand up to either of the first two on an objective level. But I'd never call it bad.
It's been a long time since I saw FF, but I remember it being one of the ones I just don't have interest in revisiting when I'm in a Trek mood (which to be fair, is a lot of the time).