One of the things that draws me to you as a friend, Huck, is that you challenge me on an intellectual level that few others can achieve.
You have the categories a bit off. 'Back to the Future' is in the same classification as MIB; science-oriented comedy. I have the book 'Lathe of Heaven', but haven't read it in over 25 years, so I can't comment upon it. Never saw the movie, or even knew that one was made. Straight SF are things like 2001, Charly, the book version of 'Altered States' by Paddy Cheyevsky (sp?) who had his name removed from the film version. Most of Star Trek was true SF, given that they had to make most species humanoid in order for human actors to portray them. (I always found it amazing that the universal translator not only changed alien speech to English, but also holographically altered the speaker's lip movements so that deaf people could understand them.
) As much as I detest Greenpeace, ST IV—The Voyage Home was my favourite Trek movie. I'm not sure if that's because of Scottie talking into the computer mouse or because of Catherine Hicks in a wet shirt. (Oh, who am I trying to kid...)
Horror/terror/psycho are a bit different, in that they are meant to scare the audience. In that regard, Alien qualifies as both horror and SF (the science was fairly accurate). There's a lot of overlap.
The main point is that true SF deals primarily with the human (or alien) condition in a setting that is scientifically plausible but beyond current technology. That's one of the coolest things about 'Charly'. It was total fiction when it was written ('Flowers for Algernon' by Daniel Keyes) and when it was filmed. The core technology that made it SF now exists.
Another thing that just fries my 'nads is the turn-around on movie rights. Phillip K. Dick wrote a pretty cool story called 'We Can Remember It For You Wholesale'. 30 or 40 years later, they decided to make it into a movie called 'Total Recall'. Once the movie hit it big, they novelized the screenplay into a book called 'Total Recall'. Same damned thing with 'Do Androids Dream of Electric Sheep', which was filmed as 'Bladerunner', and then novelized as 'Bladerunner'.
I actually have more to say about the subject, but I'm staying over at W's place tonight. She's downstairs wearing not very much, and I'm up here conversing with you. My body took a vote, and the gonads won over the cerebral cortex by a significant majority.
I'll get back to you tomorrow.