Yeah but Batman is the dark character, Superman is the bright boy scout with a positive outlook on things. I feel like the decision to make Man of Steel a dark interpretation of Superman was one of the most misguided decisions in recent film, because part of what makes the Justice League dynamic so great is Batman being the dark character, and the darker you make Superman, the smaller the contrast will be between him and Batman, and then you get two grumpy depressed dark characters for the price of one.
Even though I only thought Man of Steel was alright (not great, not bad.. enjoyable enough at the cinema, but not to re-watch) I'm still very excited about BvS mainly because of Ben Affleck and Batman. I like that the main story focuses on the destruction in MoS and what consequences it will have on Superman and the world, but it does feel like they are shoving in a bit too many characters.