It is very hard to overstate how bad “Left Behind” is. If you’re a person of faith, this airborne Rapture story might be insulting; why should you have to accept a lousy movie just because you buy the overall message? If you’re not religious, you might nevertheless feel sorry for God that this is apparently the best vehicle available to Him. Nicolas Cage (of course) plays a pilot flying a few hundred people from New York to London, until a few of them vanish without a trace. They’ve been taken—everyone eventually decides—by God, and now the hell will start. But the screenplay, performances, continuity, production values, musical score, stunts, effects and direction are all thunderously embarrassing. But that doesn’t mean you shouldn’t see it. Oh, no: Fans of bad cinema absolutely should check it out. “Left Behind” is the funniest disaster movie since the first “Airplane.” Just not on purpose.