Five years ago, I threw down a list of the five greatest sci-fi horror films ever. As usual, I was immediately bombarded with comments explaining how incomplete, inaccurate, and inadequate my list was. Inexplicable endorsements of Event Horizon notwithstanding, I spent a half-decade digesting your feedback and stand here with an amended list of the 10 greatest hybrid science fiction/horror flicks ever made.
10. Forbidden Planet

Leslie Nielsen takes a serious turn battling literally unstoppable “monsters of the id” in a thinly veiled yet still thrilling and brilliant allegory of Shakespeare’s “The Tempest.” It hasn’t aged well, especially effects-wise, but it planted seeds that bore remarkable science-fiction and horror films for the next half century. Also, Robby the Robot for the win.

9. Night of the Living Dead (1968)

The original science-creates-flesh-eating-zombies classic, it launched its own subgenre of films and gave rise to an entire generation or three of monsters. You don’t get such modern stalwarts as 28 Days Later, The Walking Dead, or (perhaps most importantly) Shaun of the Dead without George Romero’s legendary frightfest.

8. The Day The Earth Stood Still (1951)

The first person who implies the 2008 Keanu Reeves remake is the superior version gets a Gort to the brainpan. The film is an inversion of so many classic tropes: the Big Dumb Object story where the object is Earth and the tour guide is the young awestruck boy, not the all-knowing alien; a monster that is menacing in its impregnable inactivity rather than in the destruction it wreaks; and a movie that isn’t revealed as horror until the very end. There’s a reason geeks still mutter klaatu barada nikto in the presence of dangerous tech; it’s an incantation we’ve learned to fear and respect.

7. Colossus: The Forbin Project (1970)

Perhaps the first Singularity movie is also an apex of Cold War tension given techno-terror form. A generation before Terminator gave us SkyNet, we get the tale of not one but two sentient nuclear-arsenal-controlling supercomputers — one American, one Soviet — joining forces to hold the world hostage…for its own good. The subtext is razor-sharp, as is the existential terror.

6. Village of the Damned (1960)

It’s an established fact that children are creepy, but you don’t get pure-horror scarefests like The Omen or The Ring without the terrifying techno-vignette of hivemind children that parlay their parents’ unwillingness to kill them (plus inexplicable paranormal powers) into conquest of the world. The often unspoken fear that one’s children will not only overtake, but obviate us is given horrific, enduring form. Not to be shown to expectant mothers or babysitters you want to hire a second time.

5. Frankenstein (1931)

It’s campy, to be sure. Dated? Without question. But James Whale’s magnum opus almost single-handedly established the visual vocabulary for mad scientists, reanimated creatures, and homicidal creatures that are sympathetic while still terrifying. Sci-fi horror began here, and as such no list is complete without this undisputed classic.

4. Invasion of the Body Snatchers (1956)

McCarthyism taken to its absurd metaphorical extreme. Everyone is a potential enemy, and it’s only a matter of time before we all fall to the threat. Paranoia is the only rational response, and the abject horror of that “logic” is the real message of this timeless classic. The 1978 Donald Sutherland screamer remake is solid, but nothing quite matches the campy 1950s fairy tale pierced by alien invaders who turn us against ourselves.

3. The Thing (1982)

An alien that can be anyone of us is the perfect metaphor for the enemy we suspect any one of our friends or family could become — or already is. When push comes to shove, who can you really know, let alone really trust? Now magnify that with the power of an alien stalker that can turn a severed head into a giant spider. Scary is an understatement. Director John Carpenter also tacks on perhaps the most nihilistic ending you’ve ever seen in a sci-fi/action/horror film.

2. The Fly (1986)

Videodrome and maybe even Scanners could have made this list, but if you’re only going to accept one disturbing David Cronenberg meditation on the horrors of technology run amok, it’s the tale of Seth Brundle’s horrific transformation into a human-fly hybrid. The nausea-inducing effects aside, The Fly has a great deal to say about Brundle’s acceptance of, and even enthusiasm for, the monster his science has made of him. It’s a literal metaphor of humanity willfully lost in the quest for knowledge, and that’s perhaps the scariest monster of them all.

1. Alien

This requires no explanation. Ridley Scott’s masterpiece of body-violating, unknowable malevolence set loose upon a working-class crew of relatable stiffs is the apex of horror sci-fi. The inexorable, unreasoning, incomprehensible Other we all fear lurks in the darkness is given tangible, terrifying, genre-defining form thanks to artist H.R. Giger — and 30 years later it’s still the standard by which all movie monsters are judged. Alien is equal parts understated Lovecraft epic, Hitchcockian serial killer thriller, and perhaps the first real female-protagonist action film. And it’s absolutely terrifying, too. Accept no substitutes (and only one sequel, if you can help it).

No doubt, many of you will still have a bone to pick with the latest version of this list. The never-ending battle resumes in the comments section.