Some of the greatest science fiction TV shows of all time have vanished, almost without a trace. They don't get listed in articles on the "Top 50 Science Fiction Shows Of All Time." Despite achieving true greatness, they don't even get as much praise or critical attention as Alf.

Here are 10 great unappreciated masterpieces of science fiction television.

We're focusing on really unsung series here, which means the list doesn't include shows like Babylon 5, Star Trek: Deep Space Nine or Blake's 7, which get plenty of love. Also, we're not including any shows currently on the air, on the theory that they could still get more love.

10. Space Island One (1998)

Why it's unsung: This German/Canadian co-production isn't out on DVD, and all of the websites about it have been down for a few years. There aren't even any clips on YouTube.
Why it rules: This is one of the most hard-science-focused SF shows. The crew of a corporate-funded space station mostly deals with scientifically plausible problems (with a couple of exceptions) and the stories focus on the ethical problems that come with profit-focused science. Yes, some episodes are a tad slow-moving, but the best dozen eps feature high drama and high weirdness. Sample plot lines: a lonely old NASA astronaut spends thousands of dollars calling phone-sex lines from the space station. The station gets the world's last sample of smallpox for safe-keeping, and the crew debates whether to destroy it.

9. Star Cops (1987)

Why it's unsung: This show about a police squad in the "Wild West" of space stations and moonbases suffered from a cheesy title and a ridiculous ELO-esque theme tune. (Which I've sort of gotten to love, for some dumb reason.)
Why it rules: Series creator Chris Boucher wrote some of the best episodes of the original Doctor Who, and then masterminded the scripts for Blake's 7. Several Star Cops episodes feature tons of Boucher's trademark razor-sharp wit, plus the show fumbles towards a space-noir aesthetic, with the cop squad including a bribe-taker and a thuggish slob.

8. Surface (2005-2006)

Why it's unsung: Cancelled after just one season, this show about undersea intrigue failed to rope in the kind of audiences who were devouring Lost's tangled mysteries.
Why it rules: Dude, it had sea monsters! And there was a government coverup! And we had a strong female character — a scientist, even — investigating the emergence of a new and potentially world-ending form of sea life. And we never got to learn what was really going on.

7. Odyssey 5 (2002)

Why it's unsung: This Canadian show about space shuttle astronauts who witness the destruction of Earth never got enough publicity during its initial U.S. run on Showtime. It felt like an attempt to do a mature extended-cable show like Big Love, only with a science fiction premise, and it failed to reach either audience. Showtime didn't even bother to show all of the first season, until 2004.
Why it rules: The main characters are all well-rounded and flawed. And the show's set-up, in which an alien sends their consciousnesses back in time five years to try and avert the world's destruction, generates tons of potential. The show appeared intermittently on Syfy, and it's worth catching despite the inconclusive ending. The show was created by Manny Coto, who went on to mastermind the final season of Star Trek: Enterprise.

6. Journeyman (2007)

Why it's unsung: The first few weeks this time-travel show was on, its nickname was: "Gah, post-Heroes buzzkill!" The drama of Kevin McKidd struggling to hold onto his job and his marriage, while he kept slipping into the past, just felt a bit too draggy. But then something funny happened: Heroes started being the pain we endured to get to the reward of Journeyman.
Why it rules: The mystery of why Dan Vasser is traveling in time gets more intriguing, once a weird physicist starts spouting about wormholes. And all of the characters get more nicely complex as the show goes along. Most of all, though, all of Dan's meddling in the timestream has consequences he can't predict — and they only pile up more alarmingly over time.

5. Probe (1988)

Why it's unsung: This show aired opposite the Cosby show on ABC for a few months, and then cancelled during the same writers' strike that almost wrecked Star Trek: The Next Generation. And to this day, it hardly ever gets mentioned whenever anybody's bringing up classic science fiction.
Why it rules: Created by Hill Street Blues' Michael Wagner and Isaac Asimov, this show featured a scientific genius using science to solve crimes. On some occasions, those crimes would turn out to revolve around Serendib, a scientific think tank which the genius founded and then more or less abandoned. Thanks to VJMurphy for suggesting this one.

4. Star Trek: The Animated Series (1973-1974)

Why it's unsung: I know: How can a Star Trek series be unsung? But this one really is. It only recently got a DVD release, and people often skip over it in discussing Trek lore.
Why it rules: Thanks to a writer's strike that didn't apply to animation, the show managed to get some decent science fiction writers to contribute scripts, including Larry Niven and Larry Brody, plus original series veterans like David Gerrold and D.C. Fontana. The episodes are pretty fast-paced, thanks to their 22-minute runtimes, but that doesn't stop them dealing with ambitious ideas like antimatter universes, an "ultimate weapon" and time paradoxes.

3. Kyle XY (2006-2009)

Why it's unsung: This show about a genetically engineered superkid, growing up with a small family in the Pacific Northwest never got any cred among science fiction fans, and never quite got any mainstream buzz either. And unlike its fellow ABC Family show, The Middleman, Kyle XY failed to reach cult status.
Why it rules: It's a surprisingly witty show, which really develops its characters, and the romance between uber-nerds Josh and Andy is one of the greatest nerd romances ever depicted on television. Plus Jessi XX, the often ultra-violent supergirl introduced in season two, is amazing.

2. M.A.N.T.I.S. (1994-1995)

Why it's unsung: Everybody raves about other Sam Raimi television productions of the 1990s, like Hercules, Xena and Brisco County Jr. But somehow, this show about a disabled genius who builds himself an exoskeleton and becomes a superhero is never talked about. The show only recently got a DVD release.
Why it rules: It's one of a few superhero TV shows to really capture the feeling of a superhero comic, and the early episodes have a very Darkman feel to them. Later in the show's run, it becomes more Silver Age, with parallel universes, monsters and time travel.

1. Space: Above and Beyond (1995-1996)

Why it's unsung: Like many of the shows on this list, it only ran for one season, on Fox. And like the other shows on this list, it often gets ignored when people are talking about the enduring classics of the genre.
Why it rules: As veteran TV writer Jesse Alexander wrote for us a while back, this show blazed new trails and helped prepare the way for other gritty shows about space combat. The show featured "relatable, almost ordinary characters overcoming extraordinary challenges through teamwork and sacrifice." And it dealt with tough issues like the rights of genetically engineered people, artificial intelligence, and war against an alien species.

Thanks to Annalee and Meredith for the input. This list originally appeared in a different form back in 2008.