Anybody can be a businessman but the trick is to be a successful one. :) There are many qualities needed to be a successful businessman but what comes to mind right at this moment is the sign that President Truman had on his desk that says, "The buck stops here."
As an employee, it is easy to shirk responsibility and leave a problem for another person to solve. But as a businessman, every buck stops on your desk and so, every problem in your business is your problem.
I think that is one of the key characteristics of a successful businessman - the attitude that they are responsible for all the problems in their business.