In a basic definition of the gospel I think the focus should be on Jesus and should include at least 2-4:
- Jesus as God- His nature and character and role as creator
- Why we need Jesus- sin, judgment and hell
- What Jesus did for us- sinless life, cross, death and resurrection
- How we receive Jesus- faith and repentance
- Jesus' coming Kingdom- to be with Jesus in His kingdom forever in glory
The gospel is the message that God, in his love, has acted to redeem the world by sending his own Son to become a human being, live a wonderful, obedient life, take upon himself the judgment of God on sin in his death, and rise bodily from the dead, ascending to glory at the right hand of God, so that all who turn to him in repentance and faith receive forgiveness of sins and life by being united to him through his Spirit: in Jesus Christ there is salvation.
The just and gracious God of the universe looked upon hopelessly sinful people and sent His Son, Jesus Christ, God in the flesh, to bear His wrath against sin on the cross and to show His power over sin in the resurrection so that all who have faith in Him will be reconciled to God forever.
The Gospel is the news that Jesus Christ, the Righteous One, died for our sins and rose again, eternally triumphant over all his enemies, so that there is now no condemnation for those who believe, but only everlasting joy. God is most glorified in us when we are most satisfied in Him. The essence of faith is being satisfied with all that God is for us in Jesus.
You can see an updated list of all the basic definitions I have posted so far here on Google Docs.