Greatest second act ever
Bill Gates is a great entrepreneur, CEO and investor.
He is a pioneer and a visionary.
Which would already make him a great guy, but he could also be an asshole in real life, like Steve Jobs or Steve Ballmer (which are not the worst people either, but they have their big egomaniacal flaws).
Well, Bill Gates upped his game in the past 20 years with his humanitarian endeavour and effort to make the planet a better place. He has donated billions of his own hard earned money, not only that (any rich asshole can donate some writeoffs), he takes every chance to do something himself for the greater good by involving others (including head of states and governments).
His life after being the richest man in the world for many years has been more impressive than anything he (or anybody before him) has ever done before.
Getting a shitload of money is not as impressive as making the world a better place.