Most I know personally and most you read about (zuck, sean parker, even steve jobs!) were considered ass holes in some peoples eyes, but in fact, they were/are obsessed with winning. They exude an above average amount of confidence that I think rubs some people as cocky.
This doesn't mean they were horrible people.
And I know many other successful entrepreneurs - and I meet more every week through my work at GrantTree - and the best ones are not at all jerks. Some of them are outgoing extroverts, others are more withdrawn, but a quality they all tend to have is that they're friendly, approachable, polite, etc.
Now, Steve Jobs and Zuckerberg are really exceptions, I don't think you can base a general rule on them, but even Steve Jobs, if you want to take him as an example, made a very clear commitment to focus on his family. He had only 2 things to focus on: his family and Apple. I'm pretty sure he wouldn't have reviewed contracts while having dinner with his wife. His entire attention and razor-sharp focus would be on her.
I'm reminded of something an Accenture partner I once worked with said. He liked working in financial services consulting because many people in the workplace are either competent and assholes, or nice people but incompetent, and he felt that either one without the other is unacceptable.
Whether or not that's true of FS consulting, I think it's true in general: just because you're really busy changing the world doesn't justify turning into an asshole. If you act like a jerk, you're a jerk, and that's that.