The Resurrection is the gospel.
Everything else is secondary.
Paul continues the discussion of the centrality of Christ’s bodily Resurrection, witnessed by hundreds of human eyes, to Christianity. It is the one event that distinguishes Christianity from all other belief systems and philosophies. Many martyrs have died. But only one has risen. Death does not define Christianity. Life does.
For Paul, the Time of the End begins with Christ’s resurrection. It assures him that Death has been defeated and it is in the process of being destroyed, along with all earthly rule, powers, and authorities. When Christ returns, the destruction of death will be complete, never to return. The resurrection of all who have died “in Christ” is its visible proof that death has given up its dead.
Readers need to be careful to note that Paul does not address the question of what happens to those who have died prior to Christ, or who have died without knowing Christ. His audience is the Corinthian believers who hold in common the knowledge about and resurrection of Christ. To use this passage to teach that only those who are Christians will be saved misses the point.
It must be noted at the outset that the general resurrection of the dead is not Paul's concern, neither here nor elsewhere in the argument.
Another point to note is that Paul’s focus is not eschatological chronology, but the logical process of eschatology. In other words, the Christ’s resurrection as the firstfruit logically guarantees that all who have died in Christ must be resurrected. And the resurrection of believers is logical proof that death and all powers logically resulting from death have been destroyed.
The crucifixion of Christ shows the power of sin and death. If it ended there, sin and death could claim victory over God, life, and love. That’s why the resurrection, and not the cross, is the center of Christianity. That’s why the resurrection, and not the cross, is the focus of the gospel. The resurrection is the power of God at work to destroy sin and death.
Paul is thereby saying to his readers, “If Christ is not raised, then this vision of the end of all things is a lie. But Christ is raised, and we the apostles have seen him. If you deny him as the reigning Lord, you are the losers.”
The Resurrection is about more than just Easter.
Christians and Christian Churches should perhaps consider focusing more on the Resurrection and less on the Cross. The Christian faith should focus more on life and less on death. Easter should be celebrated far more often than just on Easter Sunday.
This is one of the great passages in the NT… in terms of the true significance of Easter. It is therefore unfortunate that at times this powerful demonstration of the certainty of our own resurrection is overlooked in favor of an apologetic of trying to prove the resurrection to unbelievers. First of all, that is not what Paul is trying to do. What he has going for him is the common ground of their common faith in the resurrection of Christ. There is a place for apologetics, that is, the defense of Christianity to the unconverted; but Easter is not that place. Easter, which should be celebrated more frequently in the church, and not just at the Easter season, calls for our reaffirming the faith to the converted. The resurrection of Christ has determined our existence for all time and eternity. We do not merely live out our length of days and then have the hope of resurrection as an addendum; rather, as Paul makes plain in this passage, Christ's resurrection has set in motion a chain of inexorable events that absolutely determines our present and our future.
 New International Commentary on the New Testament: The First Epistle, entry for 15:21-22.
 Bailey, location 5289.
 NICNT, entry for 15:28.