Kirk's fun to watch but his antics get a bit stale and predictable IMO. On a good day he's the ultimate hero. On a bad day, he's walking cartoon character. Sometimes he can be a little bit too perfect at his job. Shatner's cheese and ham act gets really annoying when he over does it, which way more often then I'd like. I'm really digging Pine's more subdued take on the character though.
Picard to me is the best Captain. He's what a Starfleet Captain should be. He's wise and intellectual. He'd rather avoid fire-fights if he can(there are children on the ship after all) but when the shit hits the fan he plays to win. He upholds the dignity of regulations but will find ways to get around them if he feels he has to. He listens to the advice of his officers. His heartfelt speeches and diplomacy skills are second to none. He's and idealist who believes in the better nature of hummanity. But he's a very lonely, awkward man, despite it all, who has to keep his officers at arms length because of his duty as Captain. Despite all of his accomplishments, he's the most empty man in the universe.
I'm a big fan of Sisko. Sisko, to me, really isn't a Captain. Not in the traditional sense. He's not an explorer or a diplomat. He's a soldier. He's a General. A tactican and strategist. A Crusader. He looks at the big picture and is able to see the nasty parts of the universe that threaten everything The Federation holds dear. He believes in the better Angels of our nature. But he isn't blinded by them. He does what needs to be done so Picard and Kirk can have their fun little adventures without a care in the world. He knows there are limits to idealism and diplomacy. Everything after that is what he calls a day at the office. He's the type of guy any Space Marine would gladly follow into Hell.
I'm not a big fan of Janeway. I think she plays favortism when it's not called for. I think she's overbearingly motherly to her crew. I think she makes alot of dumb calls that somehow by pure luck always end in her favor. I think she's free of having to make tough decisions that would upset the happy little cult she calls a crew. I think she and her crew don't know the meaning of the phrase "tough sacrifice". I think she murdered Tuvix so could hang out with her best buddy again.
Archer was an idiot. He's always getting captured. He's always trying to start shit. But unlike Kirk he doesn't have the brains and unlike Sisko he doesn't have the ruthlessness to get it done. His idea of diplomacy is to act really rude and condessending to his counter-part. He thinks humans should be respected and admired when they've no reason to be. He tries his best to over come that, but he never quite can. His hatred of Vulcans blinds him to reality. Like Janeway, he makes alot of dumb calls that aways end in his favor when they have no reason to.