At first glance, the choices for the Oscars' best picture this year seem to represent vibrant diversity — not among the people who made them, as Spike Lee and Jada Pinkett Smith might quickly point out, but certainly in subject and style. It’s almost as if they were meant as a historic survey of American cinema: The immigrant drama (“Brooklyn”), the international thriller (“Bridge of Spies”), the detective story, albeit with journalists (“Spotlight”), effects-driven sci-fi (“Mad Max: Fury Road”), sci-fi posing as sci (“The Martian”).