Hey there! Let's see if I can address your question.
Why do some people believe in God but not Harry Potter?
Because we know for a fact that Harry Potter isn't real. He was invented by J.K. Rowling - people can walk right up to her and she will verify it's made up.
This is a serious question. Also are any of you Christians for any reason other than a Pascals Wager?
I don't even consider Pascal's Wager a reason for why I am a Christian, although in some cases I can see why it might be useful.
Referring to the previous quote you might say, "But isn't Jesus made up too?" and I can state quite honestly, no. Jesus is not made up. Historians accept Jesus was really a Jewish man from Nazareth who died around the year AD 30. Ancient historians such as Josephus, Tacitus, and Pliny the Younger speak of him and the early followers as actual people.
I find that if it can be demonstrated that Jesus was indeed resurrected, then what the Bible says about him is true. And that what he says is true. Why? You don't just come back to life for no good reason. Jesus didn't just pass out on the cross - he was dead as dead can be. If he were resurrected, it would mean a supernatural entity, God, resurrected him.
A couple things worth noting. First, it was believed right from the outset of Christianity that Jesus rose from the dead. The books of the New Testament were written between 20 and 70 years after the life and resurrection of Jesus. Internal evidence indicates that one part of it might have come into existence within, say, 5 years of the crucifixion. This part speaks of Jesus as rising to the dead and appearing to over 500 people. It wasn't something conceived centuries after the fact - Christians from the start believed in a resurrection. In fact, all but one of the original apostles were martyred for their belief, and before that they spent many years being persecuted and hated. Would you do all this for what you knew to be a lie?
Second, no credible source outside of the Bible denies that Jesus's tomb was empty three days after the crucifixion. Sure, the Quran says Jesus didn't die on the cross, but it was written over 600 years after the events it claims to describe. There are much earlier, more reliable sources than that. Indeed, a Jewish writing called the Talmud indicates that Jesus's tomb was empty. Keep in mind, the early Jews were hardly kosher with this new Christian sect. There were claims that the apostles stole Jesus's dead body, but that is unverifiable.
So what do we have here? A man named Jesus, considered God by his followers, died on a cross, was buried, and three days later his tomb was found empty. This isn't made up - this is actual history. What happened to the body? The best explanation, out of all given, is that it was resurrected. The resurrection is God's seal of approval on the ministry of Jesus.
That's just one reason why I believe. There are other reasons, both in terms of logic and personal experience.