Yes, what is the Good News that Jesus proclaimed?
Was it him? Maybe in the Gospel of John but in the synoptics he spoke more of the Kingdom of God. That is the Gospel, the Good News.
*Luke 4:43 *
But he said to them, “I must proclaim the good news of the kingdom of God to the other cities also; for I was sent for this purpose.”
“The time is fulfilled, and the kingdom of God has come near; repent, and believe in the good news.” Mark 1:15
What it is like:
“With what can we compare the kingdom of God, or what parable will we use for it?" Mark 4:30
Who it belongs to:
“Let the little children come to me; do not stop them; for it is to such as these that the kingdom of God belongs." Mark 10:14
“Blessed are you who are poor, for yours is the kingdom of God." Luke 6:20
What is required:
“Very truly, I tell you, no one can see the kingdom of God without being born from above.” John 3:3
But it is also connected with healing:
*Luke 9:2 *
"and he sent them out to proclaim the kingdom of God and to heal."
*Luke 9:11 *
"When the crowds found out about it, they followed him; and he welcomed them, and spoke to them about the kingdom of God, and healed those who needed to be cured."
and healing is usually connected with forgiveness of sin.
"and that repentance and forgiveness of sins is to be proclaimed in his name to all nations, beginning from Jerusalem." Luke 24:47
The Gospel, the Good news is that the Kingdom of God is near and availible.
The Gospel of Mark is the most primative, the most stark. It starts with healings and parables. But the Gospel of John, coming latter has much more about Him, "I am".