Harmy said:
But then, it's a movie and it is an art form, be it 2D or 3D, so it should be the director's choice what he wants us to focus on.
You are right. But for 3D movies I think the medium could be used differently. Letting the audience choose to focus on what they want would be a side effect of using the 3D that way, indeed. And the directors would then need to shoot and edit movies with that in mind. Could close some artistic doors, but could open news ones.