"In 1999, his fortune was almost three times that of Buffett, who was the second-richest person at the time. That year, Gates’s wealth surged past the $100 billion mark"

I just ran a backtest[1] of Microsoft (MSFT) vs S&P 500 (SPY) starting in 1999 with $100 billion (dividends reinvested). MSFT would have resulted in $1.7 trillion, and SPY in $600 billion. Given the significantly higher risk of investing in MSFT versus SPY, I think SPY would have been the better choice nonetheless. Moreover, MSFT only started to perform stronger since 2016, before that, SPY was ahead of MSFT most of the time.

[1]: https://www.portfoliovisualizer.com/backtest-portfolio#analy...