Yes, there is only one gospel in this dispensation and in 1 Corinthians 15:1-4, Paul clearly states: 1 Moreover, brethren, I declare to you the gospel which I preached to you, which also you received and in which you stand, 2 by which also you are saved, if you hold fast that word which I preached to you--unless you believed in vain. 3 For I delivered to you first of all that which I also received: that Christ died for our sins according to the Scriptures, 4 and that He was buried, and that He rose again the third day according to the Scriptures.
Not to be confused with the good news of the kingdom to Israel. Jesus Christ sent the twelve to preach only to Israel. Matthew 10:5 - These twelve Jesus sent out and commanded them, saying: “Do not go into the way of the Gentiles, and do not enter a city of the Samaritans. 6 But go rather to the lost sheep of the house of Israel. 7 And as you go, preach, saying, ‘The kingdom of heaven is at hand.’ The disciples were specifically told to go only to the people of Israel, and they were not preaching about the death, burial, and resurrection of Christ.
I have explained numerous times on Christian Chat that the gospel which Paul preached is the "good news" of the death, burial and resurrection of Christ (1 Corinthians 15:1-4) and is the power of God unto salvation to everyone that BELIEVES.. (Romans 1:16). To BELIEVE the gospel is to trust in the death, burial and resurrection of Christ as the ALL-sufficient means of our salvation, yet sadly, the gospel continues to be perverted today by works-salvationists.
In Galatians 1:6-9, we see that false teachers were troubling the Galatians and were perverting the gospel that Paul received from Christ by revelation (Galatians 1:11-12). The Judaizers' perverted the gospel by "adding" requirements (laws) from the Old Covenant as necessary prerequisites to salvation and we have misguided, modern day Judaizers' today who pervert the gospel by "adding" requirements from the OT law, which results in "salvation by grace plus law, faith plus works." Paul refers to this as a "different" gospel, which is no good news at all!