For reference, their net worth is generally a measure of the market cap of a company they are largely owner in, but the proportion of that company they own.

Most of these companies market cap is tens to hundreds of times the earnings these companies make annually.

So the fair comparison would be something like, if that billionaire had a net worth that was tens to hundreds of times the size of a country.

The problem is that its a tough comparison, since the act of gaining ownership of a country isn't easy. Most countries that would be reasonably valued as a company with a market cap of 10 billion aren't just going to let you buy them or even part of them.