4. Jim Gordon
Everybody knows him by name. He's been in the comics, games, movies, animated shows. He's all over the place. He is also more important than most people give him credit for. No he's now a member of the Bat-Family, and so he doesn't get the delegation of that kind of top-billing. He is however, always there even when Batman is not. Jim Gordon, whether you or not you know it, is a key figure in the DC Universe. He has dealings with both heroes and villains alike, and is often used in comics to connect stories and drive a cross-over. As a cop he has the ability to flow through titles, and regions of the comic book world that other supporting cast members don't. Where some heroes and villains are stuck in Gotham or Metropolis, Gordon can be placed just about anywhere in the fictional landscape of DC's USA and fit well. This is what make Jim Gordon the perfect character to drive a Gotham series, and it's in him that will drive a DC Universe.