Just as there is an open debate whether or not leaders are made (or born), it seems the same to be the case within Christendom. However, Scripture is pretty clear about pastors.
Since we believe that God has created each and every one of us with a specific purpose before even time began, we probably can safely assume that pastors are born with this innate gift. God then calls them at His perfect timing into office and in most cases after a period of thorough training.
In order to have a well-functioning church according to the perfect blueprint of God, a proper pastor needs to be made in charge as the sub-shepherd of a flock. Without that kind of a pastor, the local church most probably cannot fulfill their purpose completely of being the salt of the earth and the light of the world.