Each of the companies also pays the livelihoods for tens of thousands of people, perhaps hundreds of thousands. Thats one measure of good I suppose. Opinions on net good will differ.
Gates is doing a good job at PR if nothing else. In a cynical view (that is not mine) you could see it as him stealing $100, giving away $50, and being hailed a hero.
At least, of those, Gates is doing good with all the wealth he accumulated.