The Gospel is that Jesus Christ came to save His people from their sins, and He accomplished this. I believe this Gospel because God revealed it to me by opening my eyes.
The Arminian/Pelagian gospel is that Christ came to save everyone from their sins, but because man chooses, most choose to go to hell instead of heaven. But God still loves those, and died for those who are in hell.
I am thankful people are seeing the distinctions now. One letter is a life or death difference.
Galatians 1
6 I am astonished that you are so quickly deserting the one who called you by the grace of Christ and are following a different gospel—
7 not that there really is another gospel, but there are some who are disturbing you and wanting to distort the gospel of Christ.
8 But even if we (or an angel from heaven) should preach a gospel contrary to the one we preached to you, let him be condemned to hell!
9 As we have said before, and now I say again, if any one is preaching to you a gospel contrary to what you received, let him be condemned to hell!