Few films have the legacy of Ridley Scott's space horror classic Alien. The terrifying story of a small crew being trapped in space with a killer extra-terrestrial being has spawned multiple sequels, spin-offs, video games, and comic books from the universe of the film and inspired countless others trying to mimic the same unique vision of unknown horrors in their own work. While many try to elaborate on or reinterpret the classic film, none have succeeded in recapturing the magic of Scott's film.

The sequels have the world but fail to create the same sense of dread, or one of the inspires may have an isolated spaceship with an alien attack but fail to rise above being a lesser copy. They all lack the key attributes that make Alien such a timeless film that continues to terrify audiences today. Here are some of the reasons why Alien is still the greatest science fiction horror movie ever made.

Grounded Performances

Alien chestburster scene
20th Century Fox

Space science fiction is a genre that often carries a level of elevation present in all the different aspects of its story. They deal in a world that is so far from our reality, and embrace that to make something fun and exciting. Whether it's Star Wars or Star Trek, the audience is bound for an intergalactic adventure with larger-than-life characters that don't bare much resemblance to everyday life. Alien sets itself apart by going in the opposite direction with realistic, grounded characters that feel like someone you would bump into at the grocery store.

The story supports this approach, with the crew of the Nostromo being what is essentially a team of space truckers, blue-collar workers just transporting goods from one location to another. They're not fighters capable of defending themselves from a hostile threat, just people doing a job. Scott and the casting director, Mary Goldberg, brilliantly chose to cast exclusively character actors over movie stars to support this idea that results in making the entire situation more believable and more terrifying. Seeing real people deal with such an unimaginable threat elevate the film to another level of terror for the viewer and makes the experience all the more powerful for it.

Related: Here's Why the Alien Movies Are Renowned by Feminist Film Theorists

Otherworldly Production Design

Alien-Space Jockey
20th Century Fox

Both horror and science fiction relay heavily on its production design, and Alien has some of the most visually striking costumes and sets ever made. The film consists of two very distinct locations, the grungy cargo vessel with a jumpsuit clad crew known as the Nostromo and the mysterious derelict alien ship that houses the dormant threat. To ensure the sets would be memorable, production designer Michael Seymour worked with Swiss airbrush artist H. R. Giger to create an environment that truly felt alien. Giger provided wonderfully nightmarish concept art that would act as a point of reference for the derelict ship as well as the design of the monster itself, with a unique aesthetic Giger was famous for fusing organic and mechanical material that made it a cinematic icon of terror.

Not talked about often enough is how complementary the equally famous Nostromo is to Giger's alien in its industrial design, making it an ideal location for the xenomorph to hide in plain sight. The loose wiring and exposed tubing match the monster, creating a greater sense of dread, since it could be literally anywhere. Both design choices resulted in spaces that felt very real and distinct from other space films, creating a strong visual identity that is unique to Alien.

Related: Original Alien Chestburster Scene Fascinated and Confounded Director Stanley Kubrick

Less Monster, More Terror

Ripley scared of the alien
20th Century Fox

What perhaps the most significant contributing factor to Alien being a horror masterpiece is its restraint, which wasn't an intentional choice at first. Early in production, Ridley Scott intended for the monster to be very visible throughout the film, stalking the crew through the steam-filled halls of the ship. Scott changed tactic once he saw the actor move around in the suit and immediately realized how ridiculous it looked. He instead chose to be more conservative in how he showed the creature and opted for just occasional glimpses in low light. He also worked with editor Brian Q. Kelly to cut the film down to bare essentials, creating a uniquely jarring lack of context that only tells the audience the essential information.

All of these choices create the perfect circumstances for the viewer to fill in the blanks with their own imagination of what this creature must look like and what he must do to his victims. This doubles the emotional impact of seeing it all the more terrifying, with Giger's xenomorph defying the expectations of most audience members. It becomes a forbidden image, creating a sense that just seeing it would result in death. It's a story very similar to Steven Spielberg's Jaws, which Alien was famously pitched as being the space remix of the killer shark classic. The results speak for themselves, with Alien still being lauded as an all-time horror classic that helped put Ridley Scott on the map as one of the great directors working today.