I suppose in large part my view that it's rare for SF novels to make good films takes some influence from the old canard that in Hollywood at least, only bad books make good movies. Obviously this is easy to disprove, and yet it does seem that an awful lot of minor works, from TO HAVE AND HAVE NOT to THE GODFATHER, have yielded some above-average film adaptations.
IMO, though, this is partly because those less canonical novels are more amenable to filmwriters and directors playing with them, while the Big Important Novels come, so to speak, with Canons Fully Loaded. And this may relate to why it's hard to adapt some of the canonical classics of SF, while Philip Dick is relatively easy to play with.
Take Clarke's CHILDHOOD'S END, for instance, which I re-read about a year ago. It's a fascinating novel of ideas, sort of like the SF equivalent to Maugham's THE RAZOR'S EDGE-- but it's not a very eventful novel. Any accurate adaptation to film would have to deal first with the bisected temporal structure of the novel-- starting first with how the alien Overlords approach mankind in contemporary times (not necessarily Clarke's 1953 era, but something in tune with the time of a given film-audience) and then moving forward one hundred years, to the time when the Overlords have brought peace to mankind for their own hidden purposes. That also means that no single human identification-figure can plausibly span that gulf of time, though in theory filmmakers could tinker with that detail, maybe granting an extra-long life to some character who will later do all the things Jan Rodricks does in the latter half of the novel. But then, he actually doesn't "do" much of anything but observe the Overlords' evolutionary agenda come to pass. In some ways, END would probably work less well as a full-fledged film than as a very condensed episode of an anthology TV-show like TWILIGHT ZONE.
It's certainly possible that someone could adapt certain SF novels not written by Philip Dick with success, but only with the knowledge that what works well on the page often doesn't translate that well on the screen. Again, part of this inheres in how much SF follows the example of the mimetic novel, and I imagine that anyone who manages a good adaptation of, say, CHILDHOOD'S END will have to use a good deal of visual inventiveness, as Anthony Minghella did in his not-entirely-like-the-book adaptation of THE ENGLISH PATIENT.