Iron Man has no powers, so saying that the you are not interested in the Dark Knight just because none of the characters have super powers means that you must not be looking forward to Iron Man either.
I love Iron Man and Batman, and one of the reasons is that they have built their own super identity. They were not born with it, they did not ask for it, but because of a tragedy in their lives they decide to become heroes. In my opinion that makes them more heroic than some of the other characters who have powers.
As for the tone of Iron Man, i am not worried at all. Having heard the cast and crew talk about the film in alot of interviews i am confident that the film will find a great balance between humour, drama and action.