What is the Good News or the Gospel of Jesus Christ?
The good news is that God has provided a way for all men through the gift of his Son (Jesus Christ) to the world, who came to the world to die for the sins of the whole world by shedding his blood as a sacrifice on the Cross for cleansing our sins, that whosoever will accept his gift by believing in him with all his heart and soul that he died for his or her sins and rose again on the third day, he or she would not perish but will have eternal life, a place in God eternal kingdom in heaven.
Let's explained more so that Muslims and other religions can understand.

https://www.youtube.com/watch?v=jC4CNbkeJxo