In a long post about the death of genre, Charles Stross explains why most science fiction movies are awful:
Well, the process has already begun (indeed, is well under way) in some other media: in film, for example, around 30% of the big budget movies to come out of Hollywood each year are recognizably science fiction. I mean, aliens: that’s a pretty obvious signifier, isn’t it? And Hollywood feels no need to market these movies as SF; they just are, big budget glossy special-effects beanfests featuring aliens. They’re grown-up, quite capable of finding their own audiences. But something is missing upstairs. They’re the sixty-foot-tall armoured cyborg idiot children of our genre. All fire and tantrums and no cerebral context whatsoever. There’s no internal genre dialog going on, and precious little introspection. (Yes, you can name exceptions like “GATACA”; the fact that you have to note the exceptions is itself a warning sign.)
I am not sure it is possible to write introspective, complex SF as a screen medium. The natural length of a feature movie is around 120 minutes; the traditional movie script runs at one page per minute, with 250 words per page — that buys you, in literary terms, a novella. Add in the expectations of studio executives and the dumbing-down effects of editing by committee you end up with huge pressure to make the script commercial rather than complex. Some director/scriptwriters have the clout to get what they want: but then you end up, as often as now, with George Lucas. Nor is there much scope for a dialog in which directors build on someone else’s ideas. So a large chunk of cinematic SF is stuck, spinning its wheels, mistaking ever better special effects and ever bigger first weekend box-office draws for progress.