I always hated and shivered at the idea that aliens are just someones genetic lab creation. It makes them so generic - evil experiment, monster out of control kind of thing. What I always absolutely loved was that Lovecraftian feel to them in the first film, that they are some ancient species , thousands if not millions of years old, which ended any civilization that it came to contact with and was lying dormant until awakened after millenniums by the Nostromo crew. Some naturally born ancient species from a homeworld so horrific it would be hard to visualize