Quotes by George Martin
The Gospel is a message about God and His holiness, man and his sinfulness, the Person and work of Jesus Christ, and a summons to repentance and faith. If these truths are not declared, then no matter what else might have been preached, it was not the Gospel.
There is one Gospel, and it is universal and applicable to all cultures. The Gospel is universally applicable because the one great need of all human beings is the same: they all need to be reconciled with the Creator.