The funny thing about doing a DC shared universe is that unlike Marvel, DC's characters were not created to be together. The idea to set them all in the same universe only came later. Batman and his world was literally the exact opposite of Superman and his world and so on. One way to look at it is that it was something that was forced and contrived to begin with.
However, another way to look at it is that it is was a genius idea. You have characters completely different from one another that have to come together against one big threat. They may be completely different but this is also why they work so well together and why they compliment off one another.
In other words, a DC Cinematic Universe is either going to not work that well and feel very contrived or it has the potential to be something that completely blows even the Marvel Cinematic Universe out of the water. I hope that it is the latter.