4. Time Travelling Aliens/Hoodlums
Back when gimmicks were big business for flagging World's Finest sales, the answer, like The Simpsons doing a Greatest Moments episode, was for Superman and Batman to get sent back in time. Sometimes, according to the image above (from a story involving time travel to take on some aliens who could only harm cavemen, for some reason) they even grew the same face while doing so.
Why They'd Suck The time travelling angle in sequels has been done too much. Back To The Future sequels did it twice. And more importantly, whenever it gets wheeled out in sci-fi movies, it feels like a cheap trick to manipulate and manufacture a bit more of a thrill. And on top of that, if time travel was indeed brought in for cheap thrills, it would require the story-writers to abandon the world built by Snyder and Goyer in Man Of Steel. Also, if Snyder went with the time travelling gimmick, and Superman pulled off his go-to trick of taking Batman to the past to save the world, it would simply raise the question of why he didn't do it to fix all the damage created by Zod in Man Of Steel.