Yea, people reach for this one a lot when this discussion happens. Personally, I think "but at least you're happy" is a bunch of hollow "cope" that people in the middle tell each other in order to not be so envious of the people who made it big. It's not one or the other. There exist plenty of rich people who are also happy. Happy+rich always beats happy+poor.
I'm sure there are CEOs out there who are unhappy. No doubt. But they can wipe their tears with $100 bills, and they have the option to quit their job any time they want to take up painting or become a monk to "find themself". Optionality usually beats raw happiness.