Battlestar Galactica (original)
Several TV shows tried to capture the fun and excitement of Star Wars in a weekly TV format. But none of them succeeded quite as well as the original BSG, thanks to killer robots with zig-zagging red dot eyes, cute cyberdogs, and hotshot space pilots who smoked cigars and womanized. This show is pure amazing space cheese.
Star Cops
Don't let the purposefully cheesy name fool you — this show from Doctor Who/Blake's 7 writer Chris Boucher set out to be a gritty crime drama in space. The space police force tries to bring law and order to the chaotic world of space stations and the Moonbase, and grapples with some intricate puzzles along the way. The cops include bribe-takers, idiots and film buffs — but somehow Commander Nathan Spring manages to turn them into a real police force. Sadly, it only lasted one season, and the season's first half is much better than its second. But it's still all great stuff.
Torchwood
Until a couple months ago, we would have described this show as Doctor Who's cheeky adult spinoff, full of sexual (and specifically queer) themes and lacking in compelling stories or characters. But a funny thing happened this summer — the miniseries "Children Of Earth" pushed the show in a genuinely grown-up direction, raising tough ethical questions and showing us what monsters people can be. And suddenly, Torchwood is seeming like a show worthy of celebrating in its own right.
Mystery Science Theater 3000
Not many shows can capture an important facet of fandom: science-fiction fans love to hate. And Mystery Science Theater 3000 (or "MST3K" to die-hards) made hating on bad scifi fun. "MST3K" also provided a great platform for tons of clever puns, in-jokes, pop culture references, and mocking derision of terrible movies. And on top of the consistently great humor and the fandom appeal, "MST3K" also offered a community for loyal viewers (they call themselves "Misties"). All in a format entirely untried on television (and still not duplicated to this day).
Invader Zim
Nobody seems to notice that the weird new kid in school has green skin, or that his dog is actually a robot, or that he seems bent on conquering the Earth — no one, that is, but Dib, who quickly recognizes his classmate as a poorly disguised alien bent on conquering the Earth. Most episodes deal with Zim's incompetent attempts at world domination or Dib's futile efforts to expose Zim as an alien, and the demented humor and visuals from Johnny the Homicidal Maniac artist Jhonen Vasquez elevates the alien invasion trope to gleefully black comedy.
The Six Million Dollar Man
"We have the technology. We can rebuild him." Lee Majors is Steve Austin, a spy who gets wrecked in an accident — so the secret OSI gives him a new bionic body, with fancy eyesight and juiced-up limbs. The super-spy narrative suddenly gets a new twist, thanks to cybernetics — and we get one of our first great cyborg heroes.
The Outer Limits
Similar to the Twilight Zone, this anthology series had a more science-fictional bent, with lots of stories focusing on alien abduction or strange invaders. People struggle against mysterious forces, and the moral isn't nearly as important as wondering what crazy twist lies in store.
Adventures Of Superman
There have been many Superman-themed TV shows, but the best is still probably the 1950s series starring George Reeves. Featuring advanced special effects for its day, this show pits Superman against gansters, mole people and Kryptonite-powered robots.
Stargate Atlantis
Despite being a spin-off of Stargate SG1, SGA has built up its own unique fan base. The show takes place on amilitary Gate-base in the Ancient-built Lost City of Atlantis. From there, mussy haired John Sheppard leads his team through their own Gate and all across the Pegasus Galaxy, stopping only to fight the evil alien Wraith and to trade quirky banter. Perhaps the real stand out from SGA isn't the planets, that all mysteriously look like the wilderness of Canada, or the city, or Sheppard's Cash posters — but the comic timing of the crew, especially Rodney McKay, played by David Hewlett.
Space Island One
The best science fiction show you've never heard of, Space Island One follows the crew of the space station Unity, funded by a private corporation. The show unflinchingly looks at the implications of for-profit science — culminating in a shocking final episode — and provides the most realistic look ever at life in space, including bone-mass loss. A few episodes are dull, but the show is often surprisingly weird and fun, featuring an astronaut who spends a small fortune calling phone-sex lines back on Earth, and deep-space explorers who resort to cannibalism. It also features some of the most complex, believable characters of any television show.