Let's face it - Ripley is a badass. She's not getting rescued by the hero, she's the hero doing the saving and surviving. All of this has become more popular in recent years, but with a sort of flawless-femme flavor that dehumanizes woman as much as the damsel in distress trope. Creating realistic female action protagonists is difficult, probably because it's men doing most of the writing and directing in Hollywood. I know it challenges me in my own writing. But Ripley, starting in 1979, was a unique entry into the genre. She's tough without being bulletproof, tender without being soft; in short, she's an actualized human being with a range of emotions, skills, and flaws.
And she kills Aliens. Big, nasty ones who eat Colonial Marines. The first film was so iconic that it spawned a host of imitators, including the X-Men's Brood aliens, and it could be argued that Star Trek: TNG's Data is the direct descendant of Bishop. But efforts to replicate or copy Ripley have failed, because true originals defy imitation. Much of the credit goes to Sigourney Weaver and her I'll-eat-your-children-all-of-them glare.
Hollywood's planning another Aliens feature. Because no franchise is safe. Here's hoping this entry is more Force Awakens than Crystal Skull. Otherwise, it's game over, man.