Why it could work:
The Avengers.
The prospect of putting several big-name superheroes on-screen may seem daunting, but 2012’s biggest film proved that it can be done — and done in the most awesome, crowd-pleasing way. Iron Man, Capt. America, Thor, Hulk, Black Widow and Hawkeye all managed to share the screen without things getting hokey or cluttered, why can’t Batman and Superman?
The critical success of recent Batman and Superman films
Both franchises are experiencing a wave of positive vibes and critical acclaim. It would be hard to fathom that D.C. and Warner Bros would even consider taking the risk of teaming them in a film if they weren’t committed to making sure it didn’t sink the high standards that have been set.
Nostalgia
Fans would be overjoyed just to see the two on-screen together after decades of wanting it to happen. Nothing wrong with a little wish fulfillment.