The perfect synthesis of science-fiction and horror.
The worldbuilding is refreshingly lo-fi science-fiction (the blue-collar aesthetic is a welcome innovation), the plot is straightforward (right down to the slasher-like steady elimination of characters) but smartly-told horror. The design is an unsettling mix of both, H.R. Giger’s bio-mechanical vision straddling the line of the two genres.
The social relevance (the alien as a force of rape, and Weyland-Yutani’s treatment of the crew as expandable being as dehumanising and horrific as the alien itself, with the actual alien taking the concept of “kill and absorb the value of people” to its unsettling endpoint) could have come from either genre but is stronger for having come from both.
The film is so confidently made, so fully-formed, that it’s not surprising such a large franchise evolved out of it. The film is so well-made on every level. A rightful titan of two genres. I give it four and a half facehuggers, and a chestburster.