"...if the death of Christ on the cross is the true meaning of the Incarnation, then there is no gospel without the cross. Christmas by itself is no gospel. The life of Christ is no gospel. Even the resurrection, important as it is in the total scheme of things, is no gospel by itself. For the good news is not just that God became man, nor that God has spoken to reveal a proper way of life for us, or even that death, the great enemy, is conquered. Rather, the good news is that sin has been dealt with (of which the resurrection is a proof); that Jesus has suffered its penalty for us as our representative, so that we might never have to suffer it; and that therefore all who believe in him can look forward to heaven. ...Emulation of Christ's life and teaching is possible only to those who enter into a new relationship with God through faith in Jesus as their substitute. The resurrection is not merely a victory over death (though it is that) but a proof that the atonement was a satisfactory atonement in the sight of the Father (Rom 4:25); and that death, the result of sin, is abolished on that basis.
Any gospel that talks merely of the Christ-event, meaning the Incarnation without the atonement, is a false gospel. Any gospel that talks about the love of God without pointing out that his love led him to pay the ultimate price for sin in the person of his Son on the cross is a false gospel. The only true gospel is of the 'one mediator' (1 Tim. 2:5-6), who gave himself for us."
-James Montgomery Boice