The last time Mitt Romney ran for President I wrote about businessmen in the White House and their somewhat dubious history. Herbert Hoover was a successful mining executive, kind of a management consultant of his day, known as the doctor of sick mines.
Jimmy Carter was an agribusinessman. The Bushes had their Texas businesses. Some like Ike barely touched the private sector. You can read my 2008 take here and here in the late Conde Nast Portfolio. Dated but still relevant I think.
To be fair, you could see the pre-1966 Reagan as an entrepreneur more than say a union leader. And LBJ's lifetime in government didn't save his presidency.
Would Herman Cain's business background make him a better president? Would Mitt Romney's? I don't think it hurts but the idea that one set of experiences outstrips others seems dubious.