When the reckoning of history books happens, I could see him in the running for “most positive social influence of anyone 1800-2100”.
His humanitarian work is second to none and we can expect 20+ more years of his direct influence on global policy. The world is a better place thanks to Mr and Mrs Gates.
3x gates.
If you actually do the math based on an inflation calculator, you find $5 billion: https://www.forbes.com/sites/chloesorvino/2014/07/08/whats-b...
So, the question with Gates is whether he manages to fund something that materially changes the world in a way people in the future will remember.
Saving some lives? Probably not that meaningful 100 years from now. Funding a technology that solves climate change and/or provides cheap clean energy? People will probably remember.
So it's hard to tell. Gates has funding in both areas of potential, and he's taking a very hands on approach to his philanthropy so he's more liable to get some credit, in the same way library afficionados do remember Carnegie.
Artists even more than scientists. When the Italian comedian Totò died in the late '60s this happened [1]:
> Totò died at the age of 69 on 15 April 1967 in Rome after a series of heart attacks. Due to overwhelming demand, there were no fewer than three funeral services: the first in Rome, a second in his birth city of Naples—and a few days later, in a third one by the local Camorra boss, an empty casket was carried along the packed streets of the popular Rione Sanità quarter where he was born
A similar thing happened when the Russian folk singer Vysotsky died in 1980 [2]:
> After a mourning ceremony involving an unauthorized mass gathering of unprecedented scale, Vysotsky was buried at the Vagankovskoye Cemetery in Moscow.[78] The attendance at the Olympic events dropped noticeably on that day, as scores of spectators left to attend the funeral. Tens of thousands of people lined the streets to catch a glimpse of his coffin.
I'm pretty sure no businessman on this planet would have his/her funeral attended by tens of thousands of people nor will they be interred thrice "by popular demand", so to speak.
History books will probably talk just a bit about his wealth, maybe about his humanitarian actions, but he'll definitely be remembered as the person who made personal computing a thing.
Afterwards, Gates went on to create the most effective and well-funded philanthropy since the Carnegie Foundation, eradicated Malaria, etc. While his former competitors spent their riches on superyachts and the like.