The Gospel is not simply Jesus dying on the cross for the forgiveness of sins. The Gospel is not simply a theory of atonement--or even the act of atonement itself. The Gospel is not "justification".
The Gospel is the "good news" that God has sent His Son to fulfill His original purpose for creation by "summing up everything in the heavens and earth in Him". He does this by joining His image-bearers to Himself in Christ by the Spirit thus fulfilling His purpose to reign over the Cosmos through Man in an intimate, love relationship that accomplishes the universal flourishing of whole created order.
The Gospel is the "good news" that in Christ God has recovered Sacred Space. It is the realization and manifestation of the Kingdom of God! It is the inauguration of New Creation in Christ!
Is this the Gospel we proclaim? With our words? With our lives?