I'll give you a clue it's none of those things.
Christopher Reeve did an amazing job being the man of steel for one reason. And it isn't because he looked the part. As a child growing up watching the Superman movies I believed, I mean I really believed Superman cared about me. He really cared about people. He saved people because he, I don't know how else to say it, but he saved people because he loves them. He loves life and protects all life. Like the scene in Superman 2, when the bus full of people is about to be thrown by the villains, Superman yells out "THE PEOPLE!" You really feel like he cares. I am actually one of the few people that kind of enjoyed Superman Returns. Maybe I'm a little bias, but I did find myself smiling and cheering when he caught the plane or when he picked up an entire island. But Brandon never really seemed to care. He felt like he was just going through the motions. His best scene was probably the scene with Parker Posey. The only time I felt like he cared was when she was having a "heart attack" and he was trying to help her, even if he knew she was ok.
So that's my thoughts as a life long Superman fan. We all know the action is going to be awesome, we all know the story already (which is awesome). What they have to hit outta the park is that Superman cares. He really cares about people. For that 4 year old little boy watching a Superman movie for the first time (my son) he needs to believe Superman cares about him. That Superman would save him, not just because it's the right thing to do, but because he cares about everyone. That's the Superman I grew up with.