The apostle Paul in his letter to the church at Corinth reminds that congregation of the gospel he had been preaching (I Corinthians 15:1-4): 

“1Now, brothers, I want to remind you of the gospel I preached to you, which you received and on which you have taken your stand. 2By this gospel you are saved, if you hold firmly to the word I preached to you. Otherwise, you have believed in vain. 
3For what I received I passed on to you as of first importance
: that Christ died for our sins according to the Scriptures, 4that he was buried, that he was raised on the third day…(NIV)”

 The gospel then is the same gospel today.