
Doesn't everyone believe in the same god and just call him different things?
No.
That's a common philosophy among atheists, agnostics, and people who consider themselves spiritual but don't actually follow a particular faith. It's a nice thought that basically takes all the decision-making and all the commitment out of faith.
AND, no one who really studies religion or adheres to a particular faith would agree. People who don't really know what they believe think it makes sense, but none of the major world religions agree with that idea.
Judaism believes in one G-d: Jehovah. (He has other names in Jewish scriptures that describe Him, but Jehovah is a common one.) Judaism believes that Jesus was a man - prophet or heretic - and that's all. They're still waiting for their Messiah - the Man chosen of God who will restore the kingdom of God to Israel, and whom Jesus claimed to be.
Islam believes in one god: Allah. They believe Jesus was a prophet of Allah, but not greater than Muhammad, and boldly declare, "God has no Son."
Christianity believes in the Jewish God, Jehovah, but that Jesus IS the Messiah that He claimed to be. Christianity declares that Jesus is fully man - as the Son of God - and fully God Himself.
It's a nice, comfortable idea that tries to promote peace, but it's not true.
Jesus said, "No one comes to the Father except through Me."
In Acts 4, when Peter was on trial, we read that the Holy Spirit came upon him and he preached that the name of Jesus had healed a man and, "Nor is there salvation in any other, for there is no other name under heaven given among men by which we must be saved."

