If Bruce Wayne wasn't Batman, if the Park Row Tragedy never happened, who would he be? Feel free to come up with your own theories. Feel free to tell me what you think of mine.
I personally think he'd be a better businessman than Lex Luthor. To make it interesting you have to have him run the company. The only way he could do this smoothly is if both his parents both dead. Let's say his mother died of cancer when he was eleven. His dad died in a car accident when Bruce was twenty and away at college. This version of Bruce Wayne would be just as smart the Batman we all know just not as intensely driven unless it was for competitive reasons. Also his knowlege would be in places very different. Everything he knows is to further three things: his company, his own domineering ideas about helping others, and his personal amusment. I could easily see Superman hating Bruce almost as much as Lex Luthor. Lex and Bruce would be constantly trying to out do each other. Their companies would be richer and more powerful than in cannon because of this. In this timeline half of Superman's problems with Lex are the product of the Man of Steel geting caught in the middle of Lex and Bruce's atempts to out scheme each other.
What would make Bruce different from Lex? Unselfish motivations. It's not 'Me, me, me! I want to be powerful! People will bow to me!' that he's thinking. It's 'I do it all for the greater good to make things better. If I have all this wealth and power then I must do something good with it.' Bruce's parents raised well. Those strong morals Batman has, have to have come from somewhere. Without the same tragic background though this Bruce would at times almost corrupt because of too much wealth and the power that wealth brings.
The one thing Bruce would definitely have in common with Batman would be an understanding of psychology. Bruce would be extremely good at getting people to see things his way. He would even trick Superman. He would manipulate people and most would never know it until much much later if ever. The result is actually a scarier man than Lex! The result is a man so much the opposite of the dark knight, that Batman would love to punch his lights out!
Ironically Gotham City would be a somewhat safer place. The Waynes' murder was one of the first really major crimes in the fashionable neighborhood of Park Row. Without that murder there is no quick urban decay and no Crime Alley, or at least not as much of one. Without Batman there is no Joker and Selena Kyle never called herself Catwoman. If Bruce still went to the circus that fateful night then somehow he still would have taken Dick Grayson in. An almost Batman like intensity toward protecting innocents and loved ones combined with Wayne money and Bruce's manipulation skills would be then be used to stop Tony Zucco. But Bruce wouldn't stop there. Bruce would soon control or suppress all most all of the mob activity in the city. And the fact that power corrupts would definitetly be seen.