Science fiction used to be a genre of ideas. Ever since Fritz Lang’s 1927, still-relevant masterpiece “Metropolis,” the best sci-fi flicks present us with a credible, usually dystopian, vision of our future and pose ethical dilemmas which spring from contemporary social and technological trends. Impressive visual design has always been essential — the film must tangibly create the future, after all — but action used to be merely an accoutrement to movies whose primary goal was to contemplate humanistic truths or the consequences of present day folly.