I agree with bobbart -- it's the story, stupid! One thing that bothered me in MOS was the lack of story through about the second half of the film. They just used special effects and banked on the destruction of Metropolis scene. It sounds like they are including Batman for the 'thrills' rather than for story purposes. I think they are afraid of making a relationship movie about Lois/Clark/Superman, afraid it will turn off the fanboy base. Unfortuneately, I think by just trying to 'entertain' everyone, they miss the point entirely...
Reach for the moon, for even if you fail, you'll still land among the stars... and who knows? Maybe you'll meet Superman along the way.