No offense, but Marvel has kinda been stomping DC in regards to films that aren't Batman. The real trick, though, will be just to get the right people behind it, and to unify the various efforts to make DC movies. I know some people are still resistant to the idea of a shared universe and some feel it'll just be copycatting Marvel, but it really would help keep people on track with these projects.
All of that said, I would love to see a Justice League movie.
Although, I think they should do this first:
They should see if Superman is successful. If it is, and it proves to be a good starting point (because Batman would have been a terrible one), then lead it into a Batman/Superman movie. If that does well, then pull out one or two of the other Leaguers to see how well they work. Its easy to see where to go from there.
Unfortunately, this method pretty much relies on the movies being, well, good. So if there's a bomber in the group, the effort pretty much dies.