The evidence is clear that Jesus died and was seen alive after death. As even resurrection skeptic
John Dominic Crossan said, "Jesus' death by crucifixion under Pontius Pilate is as sure as anything historical can ever be. For if no follower of Jesus had written anything for one hundred years after his crucifixition, we would still know about him from two authors not among his supporters. Their names are Flavius Josephus and Cornelius Tacitus."
As for Jesus being alive afterward, even most skeptics of Christianity grant that
1 Corinthians 15:3-8 is a nutshell of the gospel that the original Christians believed. They also grant that the passage isn't guilty of embellishment and that the statement is sincere. Therefore, in the words of Germany’s leading resurrection skeptic, Gerd Lüdemann, “It may be taken as historically certain that Peter and the disciples had experiences after Jesus’s death in which
Jesus appeared to them as the risen Christ” (
What Really Happened to Jesus, pg. 80, emphasis mine).
The question then becomes, "How could the witnesses see Jesus alive after He was crucified?" Most skeptics today, including Lüdemann, believe they merely hallucinated, but that contradicts the fact that people saw Jesus even in groups. Because hallucinations come from a person's mind, a group hallucination would itself be supernatural. If you hallucinate an apple in front of you, no one else will be able to see it. If anyone else does, the apple's really there!
Furthermore, even skeptics like the apostle Paul converted upon seeing Jesus risen. (Again, it's unchallenged even by secular scholarship that Paul was a persecutor-turned Christian who said his radical transformation was because he saw Jesus risen.) How could he hallucinate something happening that he "knew" (at least in his mind) to be false? A modern-day equivalent would be for the likes of Richard Dawkins to suddenly claim he saw Jesus, and then become a Christian.
The best explanation, though controversial for being religious, is that Jesus was really there to be seen. In other words, yes, Jesus rose from the dead.