I'd just like to say that I love this... On so many sites these days, this argument would be 140 character bickering, with most of the comments being "if you don't like it, don't watch it!" and I hate that. I loves me some good conversation, with two rational points of view. We should make this a blog and monetize this conversation! 
I think that too much is being made of The Flash, Cyborg, Aquaman and Wonder Woman at this point. From what's been said (I think by Snyder), most of those characters are hinted at, but play no large role in the movie. So what looks like a bloated superhero movie really isn't. Obviously, Wonder Woman plays a larger part than the others, but the others are mostly myths or urban legends. This is kinda how I imagined those characters being introduced when I wrote my Superman scripts, with Clark later using his journalistic side to investigate those legends and bring them into the world through the Justice League (which is a script that I never wrote).
As far as Superman goes... I don't see how Man of Steel could have been light and fun. It would take Clark a good amount of time before he reached a point where he could be anything but confused and terrified by his powers. His parents raised him to be scared of using them, because they knew that revealing those powers could be the end of him. Their point of view wasn't extreme or wrong. It was just unsustainable as he grew into an adult. The movie was about Clark moving from that point of being terrified, constantly running and hiding, and not only accepting who he is, but accepting who he wants to be. If they had made that easier, lighter, or more fun, it wouldn't have been genuine. The movie was about the biggest personal struggle that he'll ever face.
All that said, the movie was incredibly hopeful. It was about embracing who he is, but choosing what to do with it. Being born on Krypton doesn't make him Kryptonian.
I've always said that this was the Superman movie that I've always wanted to see. I do think that there is a time and place for Superman to be happy and light (not really funny, but lighter), but it would have been wrong for that first movie. That is something for him to work toward and earn. It's his happily ever after.
Civil War looks like a fun action movie, but I have a hard time watching the trailer and thinking of it as anything other than a response t Batman v Superman. I know that they had scheduled a third Captain America movie all along, but I don't believe that this was it. It doesn't strike me as character based, probably because I don't feel like the characters were ever really there. They have always used the characters like action figures, having them do whatever they needed to do in order for their movies to unfold. In The Avengers, some of the scenes of the Avengers fighting were ridiculous and out of place, but the people making it wanted it to happen, so it happened. And no matter how many times they prove that it is a bad idea, the people in these movies keep launching those stupid air bases that inevitably crash and kill a bunch of people.
It will be what all of the Marvel movies are... a thin plot, designed to have goofy characters with interchangeable personalities run around, shooting things and cracking jokes. And that works for them (money-wise), so good for them.
But when I watch the trailer for Batman v Superman, it instantly feels earned. I get why Batman is going after Superman. I get why Superman doesn't like Batman. I see how Lex is using the situation for his own advantage. And the funny part is that this isn't based on decades of knowing the characters. It's based on what happened in Man of Steel, and what we're being shown in the trailer for BvS. That's it. About two and a half hours of history with this world, and the plot of this movie feels earned.
Maybe if Civil War had been the first Captain America movie, it would have made more sense. These characters wouldn't know each other, or how to work with each other. They would be uneasy, and conflict could arise. But one of the first things you learn about using a gun is that you don't even point the thing at anything that you don't intend to destroy. I honestly can't buy into a plot where Captain America or Iron Man would intend to kill each other, and if that is taken off the table, the whole thing looks more like childish bickering than a real plot. If Civil War had been the first movie, it would have explained why those two characters bicker so much later, but earlier bickering can't explain them full-on turning on each other.
I can see Batman v Superman being the Dawn of Justice, as the title says. I can see this battle between the two known superheroes drawing enough attention to catch the eye of the others. I can see Diana stepping in when she has to, because she has the least to lose by doing so. And after her, I can see others beginning to rethink their decision to stay hidden. Aquaman may have been silent before, because keeping Atlantis a secret kept it safe from the outside world, but when worldwide events start to threaten his home regardless of whether people know about it or not, he has a duty to step up.
Cyborg was a victim, who they could say, was severely mutilated in the battle of Metropolis, and he's viewed himself as a victim ever since. But seeing what Batman and Superman do for people could inspire him to turn his curse into a blessing.
The Flash could have been helping people here and there, without ever moving slowly enough for people to see him. He is a blur that people talk about, but some may not even believe in. Some might just assume that it's Superman. But after Batman and Superman come together and Diana steps up to join them, and Aquaman reveals himself, maybe Barry would be inspired to stop being a blur and accept his role in their new world.
Mind you, all of these would be brief glimpses of characters at the end of the movie (aside from Wonder Woman). Maybe a montage of people watching the news, with these faces thrown in there. No significant roles in the movie.
Like I said, it's hard to judge what we haven't seen. But based on what I have seen, nothing about BvS feels completely wrong to me. I'm still questioning their decisions regarding Lex Luthor, but I won't know until I actually see the movie.