Aliens is my favorite because its kic*ss action, its highly quotable, lore building (a la Queen Alien), Aesthetic; I love close quarters of colonist structures and blue lighting. I was inpressed how it made dred palpable, when the marines land yoy are like “oh no.. your walking into a trap,”; the viewer is Ripley, aware its going to be bad, and that makes it frightening again, the anticipation.
I will say Alien gets into horror of facehugger, the chestburster, and Xenomorph. Alien is psychologically terrifying, even on rewatches; I get ill watching it and that is perfection, its suppose to. But Aliens feels more optimistic, you have good guys (marines) and bad guys (Xenos) which gives it its war theme; even western. It is for the reasons I said earlier and that I can watch Aliens over and over and not get ill that Its my favorite.