I recently mentioned in my "Should Spider-Man Join the Avengers?" post that I don't have much confidence in Batman Vs. Superman: Dawn of Justice, at least based on what I've heard from the rumor mill.
The movie is supposed to include Superman, Batman, Lex Luthor, Aquaman, Wonder Woman, and Cyborg. Considering this movie is supposed to continue Superman's story from Man of Steel, introduce characters who will be in the Justice League movie, do some justice to these characters, and be a somewhat good movie, it seems like this movie will collapse under the weight of its responsibilities and characters (Of course, they could go the Gotham route, and hit you over the head with obvious cameos until you feel like you have a concussion).
See, what DC is trying to do here is replicate the success of The Avengers, and create its own shared universe, and do it quickly. That's why, rather than do the logical thing and introduce these characters in their own movies (like how they did The Avengers), they decide to overstuff movies and try and rush out a Justice League movie.
It would have made more sense to connect Dawn of Justice to the CW superhero shows, since these characters are already established and Arrow and The Flash are already creating their own shared universe. It might create a bit of retconning in order to explain, but it could work.
And, ok, I'll get to the elephant in the room: Batfleck. I don't hate Ben Affleck, mostly because I haven't seen a lot of his stuff. Though from what I've heard, he's been doing some good stuff now, so that's a plus. But on the other side of that, we have Daredevil. Honestly, I'll see the movie and see how he does.
Actually, speaking of Batfleck, I should mention Batman's role in all this. From what I've heard, this movie is supposed to be based off of the graphic novel The Dark Knight Returns (it's awesome, by the way. They also did a two-part animated movie based on it that I can't recommend enough), in which Batman had retired the cowl after the death of Jason Todd, but due to an increase of crime in Gotham, he once again must become THE GODDAMN BATMAN! This story climaxes in a fight between Batman and Superman (Spoiler alert: Batman kicks Superman's ass. So, despite what some might say, Batman can defeat Superman). However, the graphic novel does not include the Justice League, (that's its inferior sequeal, The Dark Knight Strikes Again. I don't recommend it. It's just...weird...) so this movie is probably very loosely based off it. Anyway, as the title of the movie suggests, Batman and Superman are going to go cape to cape in a superhero face off, probably because of the fact that Superman destroyed most of Metropolis and killed many innocent people in battle with Zod during Man of Steel. Oops. Apparently a lot of people are a tad bit annoyed at him for all the death and destruction, Batman included. Seriously, you destroy one major city and cause countless civilian deaths, and then everybody is angry at you. People, they're so ungrateful.
I have no idea how Wonder Woman, Aquaman, and Cyborg fit into all this. Maybe they'll be glorified cameos. I don't know. We got to wait until 2016 to find out. (Meanwhile, Avengers 2: Age of Ultron comes out in 2015. Remember, kids, when it comes to live action movies, Marvel kicks ass.)