This week-- the week Arthur C. Clarke died at 90 years old-- I remarked that it was strange that so little of his work had been adapted to film or television. An acquaintance replied that he would rather see the adaptation of more classic SF and less "comic book crap."
I didn't ask him how he felt about the fact that more fantasy novels are also getting translated compared to SF novels, because I knew from past experience that he'd consider fantasy "crap" as well.
But then, as I thought about it a while, I answered my own question as to why Clarke-- and for that matter, most well-known SF authors-- don't get adapted more. And given that I've read hundreds of SF novels in my life-- probably more than I have fantasy-novels, though not single comics-issues-- I feel I speak with some authority when I say that even the best SF novels are crap-- cinematically speaking, that is.
Fantasy-fiction and comic books heroes aren't any better or worse off than SF when regarded through the Sturgeon "90% of everything is crap/crud" lens. But the fantasies nurtured in these respective genres are, without a doubt, cinematic. That means that at their best they have strong if simple plotlines that can be translated without much loss onto the screen, especially with the advent of CGI technology.
"Classic SF," however, comes out of a mimetic tradition that parallels the growth of the modern realistic novel. The content of your classic SF novel-- and here I'm focusing largely on the tradition that grew out of American magazines of the 1930s-- is no more realistic than that of a fantasy-novel, but in terms of presentation even the most excellent novels are not cinematic. Many of them are full of that peripatetic noodling called "world-building," which is pleasing within the framework of the SF-reader but which results in a lot of wordy passages that refuse to translate well to the cinematic screen.
Such a translation is possible, certainly. But where Tolkein is still Tolkien when a filmwriter leaves out some of fantasy's noodlings, and Spider-Man is arguably still Spider-Man even without Steve Ditko art, Asimov isn't Asimov without all that bookish noodling-- as should be apparent from the way the film I, ROBOT pretty much junks any fidelity to the short stories under which Asimov grouped his robot tales.
More on this later--