Just a bit bored, redoing the Tapestry 5.0.15 build. Surfing the web during the build, and found Robert Heinlein's all purpose FAQ.
Science Fiction: Stories that would cease to exist if elements involving science or technology were omitted.
This puts Star Trek and Star Wars where they both belong: in fantasy. You could "swap out" phasers for guns, light sabers for magic swords, aliens for demons, planets for foreign cities or countries, and space ships for traditional transportation and not really change the Star Wars story, or most Star Trek episodes, at all. I tend to call this "Sci Fantasy"; most older Space Opera falls into this space as well.
Cryptonomicon and the Baroque Cycle are very firmly in SF however, since both stories are driven by science and technology and even the philosophy of science and technology (and the personalities behind those who invent science and technology).
My thought here is that the movies and television, which nominally have a large bandwidth of information, are actually too narrow to portray science fiction properly. Novels and even short stories, because they can more naturally go inside people's heads and reveal their thoughts, are much more adept at capturing what makes Science Fiction about science and not fantasy. But, of course, it's always on a spectrum ... virtually any story that places actual humans on distant planets beyond the solar system is implausible to a point that borders on fantasy, even if faster-than-light travel is avoided.