A lot of the definitions of science fiction being used here are specifically for Hard Science Fiction - nowhere do the rules of society say that science fiction must be so rigorously conservative in it's use of fictive/imaginative devices, only that it is considered "hard" if it does keep them to a minimum. Classics by Asimov or Le Guin are not going to be ejected from the canon just because they use a couple of fictive things to spice up their setting (e.g. FTL, telepathy).
I know there are multiple meanings, but using Wikipedia as a guideline:
- Hard Science Fiction deals with "an emphasis on scientific accuracy"
- Soft Science Fiction deals with either "soft sciences" or are simply "not scientifically accurate"
Star Trek, Star Wars, Babylon 5, Farscape, Dune, Stargate SG1, Firefly, Warhammer 40,000 would all obviously be science fiction. Some of them are harder than others. Some of them vary by episode, with some incredibly hard science fiction being mixed in with ones containing a lot of fictive/imaginative devices. By television standards, Star Trek was on the harder end of the scale (technical manuals specifying how many megawatts of power the matter/antimatter reactor at the heart of the enterprise puts out, how the deuterium and anti-deutrium is collected, etc). Some episodes are quite hard, such as ones involving physics problems, but it has had some very soft ones too, and the movies tend to be softer than the show. I remember reading that The Original Series was so procedural and bealivable by the standards of the 1960s, with it's treatment of life in space as a profession, use of correct SI units, acknowledgment of FTL being necessary (not common in TV until the 90s, shit just 'flew' to other planets), that when shown to a test audience of science fiction fans it received a standing ovation. Some of it's social science fiction was seminal.
For fun, here is how I would place some of the big works:
*Harder*
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|- Revelation Space, Tau Zero, Red Mars, Rendezvous with Rama, Permutation City, Greg Bear, etc
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|- The Expanse, The Martian
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|- Foundation
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|- Babylon 5, Star Trek, Stargate SG1, Firefly, Mass Effect, Dune, Warhammer 40,000, Farscape, The Dispossessed, etc
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|- Star Wars
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|- Doctor Who, Space 1999
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|- Philip K Dick, Buck Rogers in the 25th Century, Lensman, John Carter of Mars, Flash Gordon, etc
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*Softer*
But truthfully they are mixed; most of them contain hard and soft elements. The best works there are all over the scale of hardness, so hardness isn't mutually exclusive with value. Star Wars, when not dealing in mystical energy fields, has engineering material and makes only a few assumptions outside science like most of the popular TV space opera. At the end of the day, labels, while a useful tool for the hard sciences, since science by it's nature is about catagorisation/discrimination, are perhaps not a wholesome way of looking at stuff like creative genre.