Wealth inequality > income inequality.

Most CEOs are closer to you and me than to the billionaire class in terms of wealth/wealth growth. And a lot of CEOs are just overpaid MBAs making sure there's a steady stream of money to the owner class, not owners of companies.
Conversely, all billionaires could get 0 salary and would still make more in a minute than you do in a lifetime, purely by appreciation of their assets/stock. Not that we shouldn't do it through progressive taxes, but nothing will change for the better if all you do is limit CEO pay, in terms of equality.