To what do we owe the second coming of the biblical epic? A genre that was once as moldy as stale communion wafers has been reborn this year, first with Darren Aronofsky’s “Noah” and now with Ridley Scott’s “Exodus: Gods and Kings.” The resurrection is partly to capitalize on the faith-based moviegoing audience and partly because the Bible offers stories suited to this blockbuster era, offering spectacle and name-brand familiarity.