Washington, Jefferson, Franklin, and both Roosevelt's were extremely successful businessmen. (though Thomas Jefferson died heavily in debt). Moreover, at the time they served in office, they continued to run their business ventures. The concept of the career politician as a primary profession is a contemporary phenomena, and I don't believe it is has served us well.
Trump has been lauded for the "art of the deal" and making incredible business decisions. However, he showed his true colors during the debate when he stated that the housing crisis was just business. This indicates that he benefited from an economic disaster. A president shouldn't take advantage of his own citizens in that way.
No, a businessman would not make a good president because there would be too many conflicts of interest. If a businessman had properties in a foreign country, he would try to do everything to make sure the property value increases, even if it ruins our relationship with some of our allies.
While it is possible for a businessman to be a good president (like most any other career field), it may be more difficult for a businessman to fit the role. In business, the main goal is to make money. It requires a mindset in which the individual is always looking to profit either for themselves or their company. They tend to find ways to make laws and other situations benefit themselves. A good president represents an entire country and has to deal with other countries as well. They need to be able to negotiate for the common good and to accept differences. This difference in the two roles would make for a difficult change.