Does Bob create $1b of wealth or do the workers of the company create that wealth?
The answer is that CEOs can be good or bad just like other types of employees, but (just like other employees) you have to pay market rate to hire one, even if they turn out to be bad.
Take a modern example, Steve Jobs, the man is the creative visionary behind most products. He envisioned the wealth and then set the workers upon creating it. Without him it wouldn't have existed.
EDIT: Look at PG's response above. same thing.