Science fiction has ruled television for over 50 years, but some shows have brightened our screens and supercharged our brains more than others. Here are the 20 science fiction shows that everybody interested in the genre should see.

Ghost in the Shell: Stand Alone Complex
Cybernetic police officer Motoko Kusanagi keeps New Port City safe from cybercriminals, maniacs and terrorists, using an array of surveillance toys that includes optical camouflage and mini-tanks called tachikomas, while she tries to get to the bottom of the mysterious "Laughing Man" incident. It's been praised as one of the most fully realized cyberpunk futures, and for having the best depiction of cyberspace environments, ever created. Plus, cyborgs with tanks versus mysterious cybercriminals FTW!

Blake's 7
Imagine a show that takes place entirely in Star Trek's mirror universe, and you've sort of got Blake's 7. The Federation is evil and oppressive, and only a gang of criminals led by a political dissident stand for freedom. At its absolute best, this show was an unflinching examination of a totalitarian society in denial. (The war-crimes trial episode is absolutely priceless) as well as an exploration into how far our freedom-fighters can go and still remain "the good guys." And it has possibly the best ending in science-fiction history.

Cowboy Bebop
This gritty, fun anime series about bounty hunters in the 22nd century probably helped inspire Firefly, and it definitely gave us one of the most memorable characters in science fiction — the super-fighter with a dark past, Spike Spiegel.

Astronaut John Crichton is flung across the universe via wormhole, and finds himself smack dab in the middle of a vast interstellar conflict between several alien races. Adopted by a misfit crew aboard a sentient spaceship, Crichton finds himself sucked into the war even as he tries to find a way home. Cool aliens (created by Jim Henson), intriguing character development, and sexy humor made this show a fan favorite for the ages.

Beautiful alien visitors arrive, promising to help humanity and provide peace and prosperity... but it turns out they're actually evil lizard people, bent on enslaving us. This always-great premise is an excuse for lots of fun paranoia, but also crazy action sequences, like a lone woman standing her ground and shooting at a spaceship with her handgun. This show made alien-fighting fun again.

Stargate SG-1
Stargate SG-1 took the successful film and managed to turn it into an insane ten seasons of adventure, by showing what happened when the military continued to use the space travel Gate technology. Richard Dean Anderson heads up a strong cast, jumping between worlds and defending Earth from alien attacks from the Goa'uld or Borg-esue Replicators. This show established Stargate as the light hearted space soap opera for anyone just looking for a laugh and a bit of suspense. Come for the cheap Gate effects, stay for RDA.

The Tick (animated)
The Tick broke down superhero conventions and rebuilt them in its own warped image. From the oddball costumed heroes (Wonder Woman and Batman somehow become American Maid and Der Fledermaus) to the villainous plots (Chairface Chippendale gets three letters into writing his name on the moon — a fact that continues throughout the series) to the Tick's superhero banter ("Spoooooooon!"), The Tick is a witty and often surprising parody.

Pizza boy Philip J. Fry is cryogenically frozen in 1999 and wakes up a thousand years later to a world of alcoholic robots, predestination paradoxes, and celebrity heads kept alive in jars. It takes repeated watchings to fully appreciate the hilariously jam-packed send-ups of pop culture in general and science fiction in particular, but you'll need a pause button and a firm understanding of mathematics to get all the jokes lurking in the background.

Battlestar Galactica (remake)
The recent BSG reimagining is many things: a theological investigation, a mirror for our current politics, and one of the best space-war dramas of all time. But more than anything, it shows what can happen when you take a great premise — the last surviving humans flee through space after a robot-led genocide, searching for Earth — and take it seriously for a change. Almost everything that's great about this version of the show comes out of treating that premise with respect, and showing how our social institutions fare in that situation.

Star Trek: Deep Space Nine
Where most Star Trek series focused on the thrill of exploration, Deep Space Nine treated the Star Trek universe as a real place, fleshing out the politics of the previous series and focusing on the special challenges of a frontier outpost. With the newly liberated planet of Bajor on side of the nearby wormhole and a looming fascist empire on the other, DS9 examined the ethics of terrorism, exposed the seedy underbelly of the Federation, and reminded us that war is hell, even in the 24th Century.

Created by Nerd Pack JJ Abrams, Roberto Orci, and Alex Kurtzman, Fringe follows the increasingly weird and transdimensional adventures of a team that investigates "fringe science" events. As the mad scientist, special investigator, and mercenary researcher get closer to understanding the science conspiracy at the heart of the tale, they discover that their own lives are bound up in it. Scary, silly, and head-explodingly gross, Fringe became an instant classic.

Babylon 5
In many ways, space opera (and science fiction generally) gets divided into two camps: before Babylon 5 and after it. Show creator J. Michael Straczynski didn't just bring novel-style, long-form storytelling to the space western — he also brought more complex characters, a deeper mythology, and a sharper-edge social commentary.

The Twilight Zone
One of the most iconic television shows of the twentieth century, Twilight Zone started in the late 1950s and launched the careers of dozens of actors (including William Shatner) and writers. An anthology series, each weird episode was introduced by Rod Serling, who usually explained its moral too. Tales of aliens, monsters, and the unknown were interwoven with noir-ish stories of people in bizarrely bleak situations. A mix of scifi an existentialism, it defined an entire generation of smart, dark SF.

The Prisoner
Patrick McGoohan's paranoid spy series about individuality and society was smart, funny, creepy and the kind of thing that people are still trying to catch up to decades later (See: AMC's upcoming revival). It's enough to make us forgive him for the subsequent years of shitty movies and Columbo guest-appearances.

Max Headroom
A fictional US drama starring the equally fictional host of a real-life UK variety show? This short-lived 1987 spin-off from 20 Minutes In The Future did more than just vault over the fourth wall with glee; it also brought cyberpunk into mainstream living rooms, and created our lifelong crush on Amanda Pays.

The X-Files
This show spawned a meme ("The truth is out there") and created a whole cult following around the duo of FBI agents investigating the weird and the outright extraterrestrial in America. But over time, its paranoia became transcendant, suggesting a much weirder and more sinister world than you'd ever suspected was also out there.

Star Trek: The Next Generation
The first live-action Star Trek spinoff served up two embarrassing years of warmed-over crap, and then a funny thing happened — the stories started getting really good, and the characters became archetypes in their own right. The Borg and Q are as much a part of science-fiction lore as anything the original series served up. By the time it ended, TNG really was the only Star Trek for an entire generation.

Buffy may be Joss Whedon's best-known show, but this is his most influential, especially for science-fiction lovers. The saga of a crew of underdogs, survivors of an interplanetary civil war, doing dirty deeds to survive and trying to keep a low profile, managed to spawn some of the genre's most memorable characters in just a dozen weeks on the air. Nobody doing science fiction today — especially space opera — can fail to be influenced by this show.

Doctor Who
One of the most iconic shows on television — period — let alone science fiction TV, Doctor Who uses its open-ended format (a man with a time machine) to tell a dizzying variety of stories. The one thing that never changes is the show's joie de vivre, in the face of horrifying monsters. The Doctor is the ultimate outsider and the ultimate hero wrapped up into one, and watching him fight evil regenerates a small part of us every week.

Star Trek
The most famous space opera of all time is also science fiction's greatest TV show generally. The U.S.S. Enterprise doesn't just explore strange new worlds and undiscovered civilizations — it explores us, our world, and the dilemmas we face as our technology outstrips our wisdom. Captain Kirk grapples with the Cold War, outwits authoritarians and zealots, and gives a little speech every episode about the human spirit — suggesting that all of our strange new dilemmas have solutions if we just follow Captain Kirk's rules to life. (And screw the Prime Directive.)

Note: This is adapted from a post we did last year, the top 100 science fiction/fantasy shows of all time. It's not just the top 20 from that post, though — we changed around the order of the shows in response to the comments we got last time. Plus this is just science fiction, not fantasy. And after watching the Lost finale, we couldn't support keeping it in the top 20 any longer. Sorry, Losties!

Top image by Sir Zeke on Deviant Art.