It's really only between Kirk and Janeway, isn't it? I mean, Picard was basically a diplomat in a more settled era, Sisko was more like a mayor, and didn't really face continual tests of courage, and Archer is an incompetent nitwit who got his captaincy either through blatant nepotism, or by rigging a raffle in his favor.
But Kirk and Janeway found themselves in repeatedly dangerous situations facing the unknown. But I give the nod to Kirk-he only had Spock as an ace in the hole -Janeway had Tuvok, the Doctor, and later Seven as a collection of super-beings.
Mayor? Sisko was the commanding officer on the front lines of the most devastating war ever depicted in Star Trek. Not only that, but more importantly, the show depicted repeated acts of bravery and heroism, including the consequences of said acts, something Voyager never did.
I know it's common to think of DS9 as the "war show," but that storyline was only during the final two seasons of the series. And I'm not knocking Sisko here, I liked the character a lot, but he wasn't out to "explore strange new worlds" nor was he trapped on the other side of the galaxy. I'm sure he was as brave as your average Starfleet captain, but he just didn't get the opportunity to show it as often as others did.