So, you want some of your classic sci-fi shows on Blu-ray? How do they do that you may ask? Well, in many cases it depends on when and where the show was created.
In the 1950s through the mid 1980s, U.S. science fiction TV was shot entirely on film. Classic shows like The Twilight Zone, The Outer Limits, Star Trek, Night Gallery, Kolchak: the Night Stalker, The Six Million Dollar Man, Wonder Woman, Battlestar Galactica, The Incredible Hulk, Buck Rogers and V: The Series all had the Hollywood look. Effects were done on film, practical where necessary, optical as required.
Then in 1986, Star Trek: The Next Generation started its seven year run. This series initiated a revolution in special effects. While live action was still caught on film, wholly special effects scenes depicting the Enterprise and the various ships and worlds it encounters would often be generated on video with the use of computer graphics imagery (CGI). CGI would often make its way into the live action as well. Unfortunately, these images would be constructed in standard definition. This method of production continued for almost two decades, every Star Trek series (except the last season of Enterprise), Babylon 5, Farscape, Firefly, The X-Files, Hercules and Xena used this method.
Finally, by 2004, shooting science fiction series on a digital format was established. The last season of Star Trek: Enterprise, the reimagined Battlestar Galactica, Stargate Atlantis, Fringe, the short-lived reimagined V, the new series of Doctor Who and Torchwood would all be shot on digital video. Doctor Who would remain in standard definition until 2010 and Enterprise's effects were still done in SD. Some outliers from this period, like Lost and the early seasons of Warehouse 13, shot on film but did the post work in HD.
In the first period, preparing the film for Blu-ray is a relatively straightforward process. Essentially it is identical to restoring any other film, an HD scan of the best elements followed by restoration techniques. In the case of Star Trek, Paramount decided to remaster or recreate the special effects in High Definition. Fortunately the Blu-ray offers either the original or remastered effects but Netflix only offers the latter. The show looks very sharp in the high definition format. There are a few episodes of The Twilight Zone that were shot on video and had to be upconverted, but the rest of the series looks fantastic. Battlestar Galactica (the original, including Galactica 80) has also been remastered on disc and the results are also impressive. Ditto for Space: 1999 (season 1 only for the U.S.)
While Doctor Who was shot primarily on video throughout its original 26 year run, the Third Doctor's introduction story, Spearhead from Space, was shot entirely on film thanks to a strike. This four-part story is as close that the U.K. got to the U.S. method of production during this time period. Unlike the U.S. productions, which were shot on higher quality 35mm film, Spearhead was shot on 16mm film. Since Spearhead was shot at 25fps, no adjustments were needed for broadcast for PAL countries. While the 2013 U.K. Blu-ray is technically encoded in 50i, it displays in 25p because there is no time lapse in the image as captured in the fields as there is in true interlaced video. However, NTSC countries expect progressive video at 24fps, so the film on the U.S. Blu-ray is slowed down 4% and the sound is pitch shifted. It is definitely as good as it will get for this story.
For the second period, the standout is definitely Star Trek: The Next Generation. Again Paramount spent the money to re-do the special effects for the entire seven seasons of the show. In the second period, the film negatives would be transferred to video and all editing, post-processing and effects work would be done there. The extra work Paramount commissioned to scan the original film into HD and recreate the effects remains the gold standard of this period. I personally find the remastered ship shots to be more natural looking than the shots done for TOS. The X-Files has also been released on Blu-ray, but that show was a lot less special effects-intensive. Lesser but still serviceable efforts from this period include Star Trek Enterprise and Firefly, which had their special effects upscaled to match their live action filmed segments. Farscape should look better than it does on Blu-ray, but the film masters apparently went missing and thus the result is an upscale throughout.
The 1996 Doctor Who: The Movie was produced in the second period format. The live action sequences were shot on 35mm in Vancouver (at 24fps, whereas all other Doctor Who material outside 3-D Day of the Doctor is shot at 50i) It was then transferred to video and edited and effects added there. When it came to remastering it for DVD, the Doctor Who Restoration Team worked with video sources. They did a reverse standards conversion, eliminating the 3:2 pulldown, then sped up the video from 24fps to 25fps, the U.K. standard. This does mean that the audio is at a higher pitch than when recorded. This holds true for the 2011 DVD remaster, which also was released in the U.S. The 2016 Blu-ray is essentially an upscale of the 2011 DVD and retains the pitch shift. The picture quality has improved modestly, but it is nowhere near the improvement you could obtain from scanning the film. Of course, in order to do a proper restoration, you would have to find the film and recreate the effects in HD.
For the third period, it is essentially a digital to digital conversion, with or without upscaling depending on the source. For the HD shows, the result is almost always watchable. Doctor Who's SD series (series 1-4) have been upscaled for HD for Blu-ray, and they look about as good as you can expect. There is far less compression on Blu-ray compared to DVD, so these releases look superior on the HD format. However, the native format of the program is 50i converted to 25p and these Blu-rays use 24p with pitch shifting. Even though there is no Only series 1 has been released in the U.S., the other series are on hold. You can obtain all the series in HD from the U.K.