In a nutshell: We don't think of Apple as a gaming company, seeing as it doesn't actually make its own titles. Yet, Cupertino is estimated to have earned more in 2019 from games than industry giants Nintendo, Microsoft, Sony, and Activision Blizzard combined.
The surprising revelation comes from a Wall Street Journal report examining the App Store's profitability and how much of it comes from games. Using Sensor Tower data, it writes that the store generated $15.9 billion between October 2018 to September 2019. Based on Apple's operating margin calculations revealed during the Epic vs. Apple trial, the company made $12.3 billion in operating profit during that period---a fifth of its overall profit.
The WSJ's own analysis estimates that Apple would have earned $8.5 billion in profit from App Store games. That amount is about $2 billion more than the combined earnings of Sony, Nintendo, Microsoft, and Activision during the same period. The publication based this on public financial records from the companies, along with an estimate on Microsoft.
It's worth noting that Apple, during the Epic trial, claimed the given operating margins were incorrect and didn't account for the many joint costs associated with the App Store, so the WSJ's numbers might be higher than the reality.
Sensor Tower reports that $45 billion was spent on mobile games from the App Store throughout the fiscal 2020 year, around $13.5 billion of which went to Apple---a lot of money, yet still only 5% of the company's overall revenue for the year. The analyst firm estimates App Store spending for the first half of 2021 alone to be $23.4 billion, $30% more than the same period a year earlier.