But it's not "new?" You can't swing a dead cat these days w/o hitting a superhero film every other month. The line-up may be unique - Superman, Batman and WW in one film - but the idea of a superhero ensemble has indeed been done before - and done relatively well.
Yeah, but people went to see 50ft tall ROBOTS that transformed on screen from cars and trucks and fought each other LOL. It wasn't about a bunch of superheros who wore tights and capes - something that even TV shows (Heroes, SV) are distancing themselves from today. Furthermore, Michael Bay knows how to make silly yet fun films that appeal to the popcorn-munching mentality of a general audience. Even Singer couldn't do that; SR was *far* from being a "fun" film (IMO!)
With JL, they may be able to distract auds for a while with a lot of explosions and wonderful VFX, but the costumed characters can't be eyeroll-worthy. Auds were sold on the robots in Transformers. Can Hammer sell Batman when people are use to seeing Bale as Bats? How 'bout Superman? Wait... strike that. I'm not going to even TRY to imagine how they're going to sell Superman when many people still think Reeve, never mind Welling or Routh. I mean, seriously? D.J. Cotrona? Pass the crack pipe. There are no words in the English language to express how pathetically ridiculous I think THAT rumored casting is for Superman.
Never underestimate the power of an "army of robots." Reference: Transformers. LOL Sometimes, good word of mouth is all you need. A great script, charismatic cast and eye-popping trailer helps get the ball rolling.
PS: I loved Transformers.