In that department FIrefly does not hold a candle to Star Trek Voyager. Roxann Dawson, Jennifer Lien and Jeri Ryan are just insanly hot.

But since we're not supposed to be talking of Star Trek, I'll list some other great space sci-fi
Babylon 5 is by far the best
Firefly was great while it lasted, and Serenity was a good movie
Blake's 7 looks cheap even compared to the original Star Trek, but it still holds up with good stories and great acting and characters
Doctor Who- well, it's Doctor Who, I'm sure it was talked about enough in other threads
Green Lantern: The Animated Series- only lasted one season, but what a season that was! The CGI animation was not great, but the writing was fantastic. Great characters, great story, had me invested like no other show in recent memory.
Crusade- Babylon 5's spin-off. Hardly worthy of it's predecessor, but I don't think it was quite as horrible as most make it out to be. Had it lasted longer it might have became something good. It had potential.

And of course there is Dune. The crazy, strange, great books (and then... some other books), the brilliant, terrible, fantastic David Lynch movie, the piss-poor new-is one, the great games (and some not so great) and above all... Jodorowsky's Dune.

LONG LIVE THE FIGHTERS!

40K and Blade Runner, but I wouldn't want to live in either, although I wouldn't mind visiting the latter :P

I could see it going for 3 seasons easy with the stories set up in Season 1. If we had 3 seasons I could better guess if it could have gone to 5 but just based on the 1 season alone I'm not so sure. At the moment it would nice if they either brought the original crew back to TV a la X-files but they would have to explain the aging and what has transpired since the last Serenity movie. Or do Season 2, Serenity 2, Season 3, Serenity 3. The End.

If Joss Whedon can make the movie sequels he sure could do it for this.

Holy shit, you have good taste! I'll +1000 to that. In fact, her whole Union/Alliance universe. And her books of Compact Space (the Chanur series). Brilliant.

I'll put my vote in for some already mentioned: Firefly, Dune, Clarke's Rama setting, Foundation, to reiterate a few.

To add to the list: Iain M. Banks' Culture novels, Peter F. Hamilton's works, David Weber's Honor Harrington series, David Drake's Hammer's Slammer's books, Lois McMaster Bujold's Vorkosigan books, John Varley's Gaea Trilogy, Larry Niven's Ringworld series, Niven and Pournelle's Mote books (Mote in God's Eye, The Gripping Hand), Orson Scott Card's Ender series (mainly the first three books for me), and Frederick Pohl's Heechee novels, just to name a few.

From video games: Phantasy Star. I am not big fan of sci-fi games but Phantasy Star has special place in my heart.

From movies: Babylon 5.

TV - Stargate.

Cinema - Alien.

Games - a lot here, but since we're talking about franchise, then - Deus Ex.

Valérian et Laureline.

I loved the John Carter books as a kid, but I don't see how it can or why it should be built into a franchise. Didn't see the movie, don't plan to.
I also loved the Stargate movie when I last saw it (idunno,15 years ago? it's probably terrible), but I don't see how it can be built into anything that I would want to touch with an 11-ft. pole.

And that's it for me and space opera franchises. I haven't seen Star Trek or Star Wars, either (I only read fan comics).

Also forgot to add, from TV

Space 1999 (pretty dated)
UFO (ditto)
Space Rangers (guilty pleasure!)

Battlestar Galactica (old and new)

From http://www.gog.com/forum/general/games_removed_from_appstore_for_using_the_confederate_flag/post267
and
http://www.gog.com/forum/general/games_removed_from_appstore_for_using_the_confederate_flag/post268 ... That's a tough question. Because many of them I've seen as a kid, and... well, some that I remember being magnificently superior to star trek turned out a bit embarrassing at second viewing. I was a huge fan of Space 1999 (season 1), and for many aspects I like it much better than Star Trek (it's less cocky, more tragic, I like its acting better, I love its premise, I like its designs better : ships, costumes, etc), but oh god the science the science. At this level it's not facepalming, it's self-beating to death.

As so I'm a bit terrified at the thought of checking the rest. The old Battlestar Galactica used to half-bore me (mostly because of the robotic kamikaze enemies), I was liking Buck Rogers a lot and I was probably hideously wrong about that (I suspect its cheese hasn't aged well).

I kinda liked the new BSG, which I expected to be real bad after the first scenes and debut promo, but it kinda suffers from being a total scam (that is, pretending to have a plot and ending up completely improvized into the most nonsensical arbitrary randomness). But I loved its style and production values and clever usage of music (very Homeworld-ish).

I've really enjoyed the Dr Who reboot, at least the first 4 or 5 seasons. I often considered it as an anti-StarTrek (for it being the absolute opposite of a military crew, and more ambivalent about humans), but it actually shares a lot of element (the crypto-political fables, sometimes painfully heavy-handed). And it lacks spaceships and stuff.

I haven't watched Farscape, Babylon 5, Firefly, etc. But I am generally not fond of the star trek approach to aliens design, shared by too many series (including Andromeda, that I discovered yesterday), and military settings easily bore me, so this narrows the possibilities.

As a kid, I loved cartoons like Captain Future (brace for retarded french title song), Once Upon A Time Space, and Ulysses 31 (still surprisingly good in hindsight, especially musically), so I wish there were more "live" series of that kind. But, meh.

So, finally, it's still mostly Star Trek (it does scifi quite right, for my tastes), and occasional movies, more than tv series. And videogames (from Elite to, even, Mass Effect or Space Quest) have very often the scifi feel that I look for. But that's still frustratingly narrow. Hence my occasionally despaired threads begging for space opera suggestions... Alas alas. Long ago, a friend used to be convinced that I'd love it, but... it didn't work on me. I didn't like its brand of not-knowing-whether-playing-for-laughs-or-seriously. But again, that's exactly what I had disliked on first contact with Dr Who, and loved afterwards. But then again, Lexx is not the same. I don't know. Maybe I should try again some day. But if I like it, I'll feel super bad towards that disappointed friend...

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In summary, I'm frustrated to not find enough movies/tv series with universes that feel the same as videogames, cartoons, or even comics space operas (I wasn't much into Valerian or Yoko Tsuno, but I was fond of the Scrameustache, back then... Became pretty lame after a while, though, or so it seems to me).

Star Trek actually had it's fair share of non-humanoid aliens, but there is only so much you can do with the likes of Horta or the Crystaline Entity. Of course there are the Changelings, one of the most important aliens in DS9, but they end up spending most time on screen in their "rubber forhead aliens" form, because again, it's hard to make good drama out of talking to a puddle. At least Enterprise gave us an Insectoid and Aquatic species of Xindi.

Simon R. Green's DeathStalker books. I'm not generally a sci-fi fan, but I dig these.

Firefly.
Firefly and Firefly.

Babylon 5 is another. STILL watch the episodes to this day.

Stargate SG-1 above all else for me, it was my childhood.

I don't even have nostalgia glasses on, I re-watched almost the whole series last year and loved it.

The Girl from Tomorrow anyone who saw it cannot forget it