Why is the gospel of Jesus Christ good news?

Volumes could be written to answer this question, but Roy King provides us with a brief four-part response: 

It is the demonstration of God’s steadfast love
Psalm 107 reveals the consistency of  God's love despite the rampant evil and destruction of this world.

It is the encounter with God’s redeeming power
Psalm 107 continues to reveal that those exposed to God's redeeming love can't help but exude gratefulness and praise for The Lord.

It is the source of joy for all people
John 16:20-24 reveals that our sorrow will turn to joy and only in the presence of our creator and savior will we fully fulfilled.

It confronts and replaces idols who rob their followers of life

1 Thessalonians 1:8-10 reveals that our purpose cannot be found or fulfilled in the things of this world, but only in Jesus Christ.

(Roy King - How Does the Church Spread the Gospel)