My favourite Sci-Fi writers:
Chris Carter - may have produced a muddled conspiracy, but there are a multitude of exceptional one-offs from X-Files and Millennium he wrote which fully outweigh this. The Millennium pilot is in fact one of the finest out there for setting mood, tone and style.
David Kemper - I think, as a whole. the writing staff on Farscape had a wonderful dynamic, yet list all of Kemper's episodes and you'll see that the vast majority of the brilliance came from his keyboard. Sure he had many of the pivotal arc episodes, but that didn't stop him writing some of the finest character moments on the show. And, heck, ALL TV writers need to take a lesson from him about how to write romance convincingly. His writing of John and Aeryn is one of the most real and complex TV romances full stop.
Ira Steven Behr - Big ideas, big pay-offs. One of the grander SF TV writers building cities in the sandlot whilst others settle for little castles.
Ron Moore - again, loses it in the bigger picture, but his writing can be devestating. With the ability to write wonderfully silly stories like Take Me Out To the Holosuite and In the Cards, and then throw out a Rocks and Shoals, or Occupation is remarkable. In fact his his finest writing for me came out of Carnivale, with Pick a Number and The Day That Was The Day. Needs to rein in his ego somewhat, but when he puts out something like the pilot to Caprica, then I'll give him some latitude.
Joss Whedon - he's certainly a love or loathe him kind of writer given, no matter what he scribbles, it has it's own sence of flippancy and dialogue-patter. Still, heck of a show runner and episodes like The Body, Once More With Feeling, The Gift, Becoming, Objects in Space and A Hole In the World, punch him up into the upper echelons for me.
JMS - his dialgue might be hokey, his plotting a touch convenient at times, but Babylon 5 is a hell of a show, flaws and all. Everything that is good about JMS is in there (HUGE ideas, deep spirituality, tenderness and high tension), as is everything that is bad (a tendancy to over-reach, jingoistic rah-rah "we will win it all" themes), but in the end it's a huge, sprawling complex series that deserves to be near the top of anyones list, as does JMS himself. Though it doesn't match it for grandeur, Jeremiah also shows off some of JMS' writing skills (and foibles).
Rene Echevarria - the unsung hero of DS9 for me. Whilst RDM and ISB were bashing Roddenberry's idealistic Trek universe against the wall, Echevarria constantly tapped into the romanticism of the universe, grounding the characters and making them not only relatable, but loveable too. This trait has come through other shows like Now and Again and Medium, where a real sense of heart shines from the characters. A wasted talent on Terra Nova.
David X Cohen - Head writer of Futurama and on listening the commentaries, clearly the guiding light for most of the character relationships. Whilst the show regularly plays pin-ball with wonderful sci-fi and physics theories I feel he kept it all in check by making us love them all, even the tiny characters like Scruffy.
Michael Piller - hell of a writer, hell of an ideas man, and more importantly, hell of a leader.
Tim Minear - or as I like to call him "The Man That Made Angel". There is no doubt that he and Joss Whedon riff off each other to an almost combustible level, but for me, his work on Angel and Firefly made those shows. On top of that his production of Wonderfalls (and the episodes he wrote) and heck, even The New Adventures of Superman show a continuous level of talent for making the daftest of ideas palatable. The man has had disasterous luck trying to get other shows off the ground (as either creator or showrunner), with wonderful off-beat shows like The Inside, Drive and Terriers dying quick and painful deaths, but all of them have his quirkiness and off-kilter view of their respective universes.
I could go on but these are the SF writers I love and will go out of my way to watch if they produce new material, genre independant.
Hugo - waffler