There's only one Gospel, the Gospel of Jesus Christ, which is the Gospel of the kingdom, the Gospel of God's grace.
St. John the Baptist's ministry was a ministry of repentance, a calling of people to repentance in the expectation and hope of God's coming salvation through the advent of the Messiah. John's ministry pointed toward Christ, pointed toward the Gospel of Jesus Christ. And thus the hopeful expectation of redemption can be said to be Gospel, in the same way that when the Prophets point forward to redemption and God's saving promises it is Gospel.
But the Gospel is never Law. God's commandments are not Gospel, but Law. Which is why the Law cannot justify, it cannot produce faith. Thus any who argues that the Gospel has anything to do with commandments, obedience, and good works preaches a false gospel.
The Gospel has nothing to do with our works, it has nothing to do with God's commandments. The Gospel is always good news. The Law has no good news. There is nothing in the Law to comfort the weary sinner who transgresses the Law.
The murderer receives no comfort when the judge declares, "You are guilty". The murderer receives only the cold hard truth of their own guilt and condemnation under the law. The Law isn't meant to bring comfort, but to condemn sin and reveal the guilty verdict against all of us.
The Gospel is the verdict of "You are forgiven, your debts are paid in full, your guilt is wiped away".
If you aren't preaching the forgiveness of sins and the reconciliation between sinners and God through the death and resurrection of Jesus Christ, then you aren't preaching the Gospel.
If you are preaching the commandments of God, to love our neighbor, to act justly in the world, etc, you are preaching the Law. Which is necessary, because we are guilty of sin, and that sin is serious--therefore, we are to repent.
But each must be preached correctly and rightly; confusing Law and Gospel breeds theological turmoil and spiritual death. The result can only ever be pride or despair. But never faith, hope, and love.
Faith is borne of the Gospel. Hope is found in God's promises and the comfort of His promises. Love is found in the freedom of conscience to love our neighbor without being enslaved to a guilty conscience before God believing that we must somehow earn God's favor, acceptance, and compassion through our meager works.
Man instinctively rebels against this because man, a slave of his disordered passions, always wants to assert the theology of glory by good works; because the message of the Cross is foolishness to the world and to the natural man. We preach the foolishness, humility, and weakness of God in the Cross, a stumbling block for the Jews and foolishness for the Greeks.
Men, who love to boast of their works, and glory in their works, at once both despises the Law of God because it calls him out as a sinner; and hates the Gospel because it robs man of his "natural rights" to be his own lord. Because the Law means we are wretches, naked beggars. The Gospel means that God freely gives everything to such a wretch and beggar, clothing him with the righteousness of Jesus Christ, and working faith in him by which the beggar's hands are opened, and receive everything from God.
To say that I have nothing except what God gives me. And I am nothing except what God makes me.
I am a sinner.
God calls me a saint.
I am a slave.
God calls me free and His own child.
I am wretched.
God calls me blessed.
I am poor.
God calls me rich.
Before the Law I am all these things: A sinner, a slave, a wretch, and poor.
By the Gospel I am called a saint, a child of God, blessed, and abundantly rich in Christ.
These are simultaneously true: I am a sinner and I am a saint. I am a slave of my disordered passions, and I am the freeman of God in Jesus Christ, adopted as a beloved child of the Father. I am a naked wretch with nothing, poor, a beggar, hopeless and hapless; and I have been made rich by the countless blessings of God's mercies which are poured out abundantly upon me day and night in Jesus Christ our Lord.
The Law calls me a sinner.
The Gospel calls me a saint.
Both are true.
-CryptoLutheran