Given some of the stuff coming out after his death, it seems to be more of the case he didn't satisfy people's need to hear about it as opposed to doing it. And since he died very early, we will really never know what the final word would have been.
I guess I would be a horrible billionaire too, since my father taught me it is impolite and improper to brag about giving. I can see why Gates does it (publicity is needed to make his goals), but that is not always the case (and sometimes, it messes up what you try).
I have heard that he'd become somewhat less of an asshole in his later years, and I know he reconciled with his daughter at some point. I hadn't heard about stuff coming out after his death, though. I'd like to see a source on that.
I think there's a big difference between someone who blatantly broke the law, like Horiemon, and someone who failed to contribute as much philanthropically as people would have liked to have seen (Jobs). Moreover, we have examples of successful entrepreneurs who have given back (such as Gates).