> There's also the fact that the giant humanoid alien should have died in the crash and still be sitting in his pilot seat rather than getting up and chasing the heroine of the film only to die elsewhere.

That was the bit that seemed to be about to dovetail into the first film, but didn't. I guess we have to assume that the Nostromo crew found a different ship, piloted by a different alien, probably crashed in a different way on a different planet. In which case, what's the bloody point of this prequel at all?