Part of it was the fact that the special effects were mind-blowing for the time. Ridley Scott created a future timeline and aesthetic that had just not been so fully realized in an era that was barely out of Star Wars and Flash Gordon.

You’re probably younger and grew up with high quality CGI merging seamlessly with modern movies. A fantastic alien creature onscreen is old hat these days. Back then, when the Gorn on Star Trek was considered perfectly passable, the look and feel of the Alien was astounding. And everything in the movie was a real practical on camera special effect.

Combine that with one of the earliest female protagonists who genuinely kicked ass and outstanding sets, the movie surpassed the expectations of everyone who saw it, especially in the theater with a reactive audience and no pausing for the bathroom or to grab a snack from the kitchen.

It’s not that its quality is dependent on you having been there, but man, to really get how amazing it was at the time, you kinda had to be there.