I don't think the DCEU should have a "lead" character a la Iron Man or Wolverine, that gets stale quickly. If there has to be one though, Wonder Woman is the obvious choice all comics history be forgotten. This Superman is a sulking moron whose inner life consists of other people telling him how to feel and what to do, while standing there silent, offering no insight of his own. This Batman is an unrelieble psychopath, only rivaled by the Joker on how likely he is going to murder everyone involved.
I'm joking, but still, damn Wonder Woman is so important to this franchise.
If anyone should be the strong silent type out of those two, it should be Batman, at least when Bruce Wayne is in his Batman identity, and not Superman. Superman should be far more chatty and outgoing, and as a journalist, have many more opinions. His personality should be more like Gal's Wonder Woman who displays compassion and more of a zest for life. But in reality, as he has been portrayed so far, he is definitely a little too passive and introspective and rather economical on words.
I don't know how well this Superman relates to children or if he would feel awkward around them, or whether children would want to either be around him or look up to him. He doesn't exactly feel approachable at all, which is what Christopher Reeve was, and what Gal is as WW. Gal is extremely accessible and her WW seems like she would love being around young people and being a role model to them.
The thing about leadership is that it can't just be a function (in terms of giving out orders or strategising). It also has to be about character, being willing to serve others and leading by example. Also about how well they relate to others, especially the "little people", and how much of a sense of trust they immediately engender.
If you were to have the Justice League stand up in the United Nations or any diplomatic peace mission, would you really put someone like Superman or Batman up there as they are in the DCEU? Or if the League have to present themselves to the public as a force who can be trusted and are definitely on humanity's side, who would you get to be that public face?
WW is the one with the best people skills who naturally relates to others and immediately engenders trust. There is nothing aloof about this WW, which is exactly what you need. If Superman had been like his traditional self, he would not have been aloof, but this one is remote and transcendent and feels almost removed from humanity rather than having really gotten down to their level to show that he is one of them (even if he is really an alien).
And from a business point of view, it just makes sense to capitalise on Gal's popularity and WW's success. Again, she is the most approachable and people person out of her, Affleck and Cavill and the one who conveys the most enthusiasm.
