What's the gospel?
1. The kingdom of God is replacing the kingdom of the world. "[Jesus] said, 'The time is fulfilled and the kingdom of God is at hand. Repent and believe the gospel!' " (Mark 1:15).
By "the kingdom of God" we mean the kingship of God. That is, the Greek word does not refer to a place (like the United Kingdom) but to God's status and authority as king. The kingdom of God is the reign of God.
That God's kingdom (kingship) has come is good news, because it means that the rightful Ruler of Earth has reasserted his royal power and prerogative in the face of the usurping rebel, Satan, and all the sinful angels and humans who have joined in his rebellion. We live in a lawless, chaotic, unsafe place. But there is good news: God's kingdom has returned and is reestablishing law and order for the good of the world. An angel in Revelation says, "In the days when the seventh angel is about to blow his trumpet, the mystery of God is completed, just as he has proclaimed [literally 'evangelized' or 'preached the gospel'] to his servants the prophets" (10:7). When the seventh angel finally does blow his trumpet "there were loud voices in heaven saying, 'The kingdom of this world has become the kingdom of our Lord and of his Christ, and he will reign forever and ever' " (11:15).
It is fitting that Jesus announces the coming kingdom when he comes because he personifies the kingdom. He is both the King of the Jews and the first, obedient Servant of God. If the kingdom is God's authority made manifest, Jesus is it. He is the executor of God's authority (as in casting out demons for instance) and is subordinate to God's authority (doing the Father's will at all times, even to the point of death), which makes him worthy to be exalted above every name. "The glorious gospel of Christ, who is the image of God," is that "Jesus Christ [is] Lord" (2 Cor. 4:4-5; also Acts 10:36).
The kingdom of God is replacing the kingdom of the world in Jesus Christ. That is good news.