BUT! What really bugs me is all the teriffic SF stories that have never been done or done badly.
Ugh, yes. I've just read I Am Legend (Richard Matheson) and it's a great book, but both the films I've seen - Omega Man (which is bonkers and Heston does his usual) and I Am Legend (Will Smith as hero? Pah, not in the book!) - have been terrible adaptations. If only someone would make a literal version of the book, it would be fine. I suspect something of the tone and subtext puts them off, but then Hollywood hardly puts out pristine beacons of perfect humanity. Someone good would have to do it. One can hope.
PK Dick's Through A Scanner Darkly was an intriguing film. I haven't read the story so can't compare, but it at least seemed like the film was made by someone who knew their onions. Must read it and find out.
Even Bladerunner, though a classic and a fine film, was bugger all like the book. Totally, utterly, different beasts.