All right, so James Cameron delivered the textbook case for creating a sequel that can stand on its own without merely copycatting the original (“Aliens”). He made science fiction smart and rousing in the relatively low-budget “The Terminator,” then pioneered morphing visual effects in its sequel, “Terminator 2: Judgment Day.” He launched modern cinema’s biggest blockbuster with “Titanic,” dominating the Academy Awards and luring teenage girls back to see it again and again to pine over Leonardo DiCaprio. But what’s he done for us lately?