From Billy Abraham’s Divine Agency and Divine Action: Systematic Theology v.3:

The heart of the Gospel is the astonishing news that God has inaugurated his kingdom in the life, death, and resurrection of Jesus of Nazareth. We begin not with the creeds or with some moral code but with an announcement: “The time is fulfilled, and the kingdom of God has come near; repent, and believe in the good news.” The fundamental image in play is political; God’s sovereign rule in creation and history has come in a fresh and powerful manner. Yet the fuller content of that message transcends politics and cannot be reduced to politics. The content reaches back into eternity before creation in the councils of God and it stretches forward beyond history into eternity with a radically transformed creation. The kingdom is partially already present in creation and providence; it took specific shape and promise in an everlasting covenant with Israel; it has become radically present in Jesus of Nazareth; it is brought close since Pentecost through the work of the Holy Spirit in the life and practices of the church; it spills over into every nook and cranny of the world; and it will be fully realized for humanity and the cosmos in the future.

The gospel – the good news – is news, the announcement of something something that has happened. That which has happened is good news.