In brief: In Kersey Graves' book "The World's Sixteen Crucified Saviors", 20 questions are asked. An attempt will be made to answer each of the following as precisely and effectively as possible. The information of this book comes from Infidels.org at this link.
1. There were many cases of the miraculous birth of Gods reported in history before the case of Jesus Christ.
2. Also many other cases of Gods being born of virgin mothers.
3. Many of these Gods, like Christ, were (reputedly) born on the 25th of December.
4. Their advent into the world, like that of Jesus Christ, is in many cases claimed to have been foretold by "inspired prophets."
5. Stars figured at the birth of several of them, as in the case of Christ.
6. Also angels, shepherds, and magi, or "wise men."
7. Many of them, like Christ, were claimed to be of royal or princely descent.
8. Their lives, like his, were also threatened in infancy by the ruler of the country.
9. Several of them, like him, gave early proof of divinity.
10. And, like him, retired from the world and fasted.
11. Also, like him, declared, "My kingdom is not of this world."
12. Some of them preached a spiritual religion, too, like his.
13. And were "anointed with oil," like him.
14. Many of them, like him, were "crucified for the sins of the world."
15. And after three days' interment "rose from the dead."
16. And, finally, like him, are reported as ascending back to heaven.
17. The same violent convulsions of nature at the crucifixion of several are reported.
18. They were nearly all called "Saviors," "Son of God." "Messiah," "Redeemer," "Lord," &c.
19. Each one was the second member of the trinity of "Father, Son and Holy Ghost."
20. Several Christian doctrines existed in earlier religions.