Well I'll quickly give you the three things that most convinced me.
Undoubtedly someone will have objections. Also note that I'm only going to scratch the surface quickly.
1. Biblical Prophecy
2. The reliability of scripture
3. The Resurrection1.
re: 1. I don't have the time to dig for this information right now, but the prophecies of the Bible are uncannily convincing. The Bible predicts, some 600 years before Jesus, a man born of a virgin, a suffering servant, that dies of CRUCIFIXION (mind you, this method of execution had not been invented at the time of the prophetic writing), a man born in the line of David, the exact time of Jesus birth, the place of his birth, and many many other things. It's overwhelmingly convincing and as a rule, Christianity is the only religion that can boast on this enormous stage.
re: 2. The New testament, in particular, has been tested and observed so much more than any other historice text it's frightening. Yet, with absolute flyng colors it passes every test given to any historical document whatsoever. I've spoken about these here before and I'm sure I'll be asked to again. It's proven absolutley reliable.
re: 3. This is the big one, and the clues to the truth are overwhelming. If Jesus rose from the dead, then everything changes. Did he?
First, let's understand some historical events.
The tomb must have been empty and here's why. In 1 Corinthians 15 Paul (15-20 years after Jesus) Paul speaks of 500 witnesses that saw the resurrected Christ. If these witness did not exist, this new religion would've been utterly destroyed. "Paul is a liar! No witnesses can be found!" That never happened.Additionally the way the Bible portrays the resurrection would've been the last imaginable way anyone would've made it up at the time! For example, the first eyewitnesses (according to the Gospels) were women. Women's low social status of the time even made their evidence inadmissable in court! Why would the writers of the Gospel have women be the first eyewitnesses for any reason other than it actually happened?
NT Wright argues, "the empty tomb and the accounts of personal meetings with Jesus are even more historically certain when you realize they must be taken together. If there had been only an empty tomb and no sightings, no one would have concluded it was a resurrection. They would have assumed that the body had been stolen. Yet if there had been only eyewitness sightings of Jesus and no empty tomb, no one would have concluded it was a resurrection, because people's accounts of seeing departed loved ones happen all the time. Only if the two factors were both true together would anyone have concluded that Jesus was raised from the dead."
The tomb MUST have been empty. Skeptics could have easily produced Jesus' rotten corpse were it not. The main argument then is, then maybe the disciples stole his body and the "eyewitnesses" just went along with it. To that, Keller says, "The assumption behind this very common hypothesis is a form of what CS Lewis has called "intellectual snobbery." We imagine that we modern people take claims of a bodily resurrection with skepticism, while the ancients, full of credulity about the supernatural, would have immediately accepted it. That is not the case. To all the dominant worldviews of the time, an individual bodily resurrection was almost inconceivable."
So what happened? An explosion of a new worldview. How do you explain it but that this Jesus person was bodily resurrected, and witnessed by 500 people in actual history.