Well, ALIEN 3 was mostly shot in England and Stanley was just recently recognized as a sci-fi director at the time - HARDWARE came out in '90, Fincher started shooting sometime in '91, I think. Before him, there was a revolving door of a few directors; Renny Harlin and Vincent Ward, at least. UK is a relatively small shop when it comes to genre filmmakers; Stanley might've very well been approached at some point to take over the reins, based on the success he had with HARDWARE.
At the time, I think he had DUST DEVIL quite firmly en route to production. Mind you, he did that with JUDGE DREDD at the time, which back then was a UK flagship for sci-fi - that is, before people saw the end product. So while I can't speak for Stanley's behalf on this, what I can say is that there was a good chance he was met by the producers on the job. If so, he might've opted to do the commercial instead, as I believe Fox's pay might've been quite good and he'd have the chance to tackle a bit with the famed source material without going through the same treadmill Fincher had to put up with.
Stanley's comment on JUDGE DREDD might lend credence to this scenario: "
At that time Dust Devil was happening, but also I was getting very wary of getting involved because it's a bit like Batman, the margin for creativity is a bit on the slim side. And after RoboCop and Mad Max, you couldn't really get the character anywhere that someone else hadn't been before." -
Fangoria 125---
I can wholeheartedly recommend the workprint of ALIEN 3 to anyone interested in the series. While still far from perfect, the 2.5 hour version
actually makes sense and has whole lot more of character development. Plus, Paul McGann (The I of WITHNAIL AND I) now has a larger part as a suitably quirky convict.