Shatner even speaks in that over the top way - he's a Shakespearian trained actor, and that seems to have melded with him so deeply, he's always in "declamatory" mode!
My fave Captain is Picard, without a doubt. He was more of a leader. My father always used to say that Picard realised that his position was more than personal aggrandisement - Kirk wanted to always be in on the action, whereas Picard knew that he was more valuable on board ship, rather than with the away party.
Both, however, did have the necessary nerve needed for a leader in that situation, and they both listend to advisors, but always made their own decision. Picard, though, is more distant from his crew than Kirk, and also seems more "human".