Let's be honest though: the stuff Gates is doing today is way more important than any of the things Jobs did over the last decade. We can argue about the relative merits of disrupting the cell phone handset industry and tablet computing, long-tail effects thereof and the like, but at the end of the day the best you can argue is that it will have trickle-down effects for the poor and disadvantaged.
Gates, on the other hand, is working on goals to directly improve the lives of people. And the people his foundation is trying to help tends to be the folks who need help the most, not people who can afford expensive mobile phones and even more expensive mobile phone rate plans. Gates is no saint by any means, but I can't see how after working on such big-picture issues, he'd want to come back and run a business.