Now watch closely...
1Cor 15:1-11
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,
Was this a special unique gospel that was given to Paul, like madists assume?
Nope
Read on....
5 and that He was seen by Cephas, then by the twelve. 6 After that He was seen by over five hundred brethren at once, of whom the greater part remain to the present, but some have fallen asleep. 7 After that He was seen by James, then by all the apostles. 8 Then last of all He was seen by me also, as by one born out of due time. 9 For I am the least of the apostles, who am not worthy to be called an apostle, because I persecuted the church of God. 10 But by the grace of God I am what I am, and His grace toward me was not in vain; but I labored more abundantly than they all, yet not I, but the grace of God which was with me. 11 Therefore, whether it was I or they, so we preach and so you believed.
Whether it was Paul or the other apostles who preached to the Corinthians, it didn't matter to Paul. Therefore the other apostles preached the same gospel. Mads assume that it was only Paul's job to preach his gospel to the gentiles, but Paul himself said, "so we (Paul and the other apostles) preach, and you believe".
Believing the one gospel is what's important, not the person delivering it. It could have been Peter or James, but it wasn't, it was Paul.
Acts 15:8-9
"So God, who knows the heart, acknowledged them by giving them the Holy Spirit, just as He did to us, "and made no distinction between us and them, purifying their hearts by faith.