The proof that I might not be so far off the mark is this, if the author of this post is to be believed. In short: Giger struggled with night terrors. A form of therapy for him was to keep a sketchbook next to his bed and draw the things that caused him such anguish. The design for the alien is based on a painting (based on a night terror) by the title of Necronom IV, pictured in that link. In a very real way, the alien is a painting of anxiety and fear.
And this is what I think the Alien Anthology has to contribute to the idea of Science Fiction: transcendence is out there, waiting, but the path is littered with failures, and the cost of transcendence is terrifying and there’s the very real possibility you might not make it. But Ripley made it, and it literally cost her life (arguably seven of her lives). Skipping right to Alien: Resurrection, because movies two and three are just explorations of the first while Resurrection offers a new insight, Ripley achieves a kind of transcendence. Knowing what we here in 2014 know about the Alien universe, we know that the xenomorphs (as the second movie comes to call them) aren’t just terrifying space murderers, and they aren’t even the final reckoning. Rather, if the vision of Prometheus is to be trusted (though it is ever so briefly hinted at in the first movie), these xenomorphs are the most upsetting road signs on the way to a final transcendence: reunion with our creators.
Knowing that, and assuming you’re wont to take all five movies as contiguous commentary of the same universe, then it’s possible the only way there is through our Christ like death. A very literal dying to self in order to be united with our fears. That union allows Ripley, and could allow us, to push deeper into the unknown. But Resurrection comes with a powerful caveat: Ripley might have evolved, but so have her fears. Her fears have come to know her so well that they can mimic her, manipulate her, they know how to get from her what they need. Not only does she evolve, but she has to relearn how to be smart in the face of these limitations.