Batman / Bruce Wayne
If there is an eccentric billionaire I would vote for, it would be Bruce Wayne. I'm sure the business side of him does some underhanded things, as much as any other major corporation, but he does try to take care of the orphans of his fair city and donates a lot to various non-profits. Plus, when it turns to night, he fights crime with some bad-ass gadgets and invokes fear in everyone that would commit a crime that night.
Also, unlike Superman, he doesn't need to level a city to defeat a super-villain.