In 1875, Kersey Graves wrote a book about mythical parallels to the Christian story of Christ. No one has yet produced a comprehensive review of his argument. A good, but brief, review of the book is here, by Richard Carrier: “Kersey Graves and the World’s Sixteen Crucified Saviors.” Basically, Carrier reports that Kersey Graves was very sure of himself; but he cites few references, makes assumptions, and blurs distinctions. Myths of journeys to the Underworld are not similar enough to count. Sometimes his parallels are from well after the time of Christ and could be based on the Christ story. He also uses the parallel of Christ’s solstice birthday being the same as for many sun gods. But we know that Christ was given that birthday around 300 A.D. for cultural and political reasons. So the book is not reliable. See the review for other problems with Graves’ methods and conclusions.
However, there are two early early examples of death and resurrection that Kersey Graves did not mention. the Thracian God Zalmoxis and the Sumerian Goddess Innana.
Carrier describes them as follows:
The only pre-Christian man to be buried and resurrected and deified in his own lifetime, that I know of, is the Thracian god Zalmoxis (also called Salmoxis or Gebele’izis), who is described in the mid-5th-century B.C.E. by Herodotus (4.94-96), and also mentioned in Plato’s Charmides (156d-158b) in the early-4th-century B.C.E. According to the hostile account of Greek informants, Zalmoxis buried himself alive, telling his followers he would be resurrected in three years, but he merely resided in a hidden dwelling all that time. His inevitable “resurrection” led to his deification, and a religion surrounding him, which preached heavenly immortality for believers, persisted for centuries.
The only case, that I know, of a pre-Christian god actually being crucified and then resurrected is Inanna (also known as Ishtar), a Sumerian goddess whose crucifixion, resurrection and escape from the underworld is told in cuneiform tablets inscribed c. 1500 B.C.E., attesting to a very old tradition. The best account and translation of the text is to be found in Samuel Kramer’s History Begins at Sumer, pp. 154ff., but be sure to use the third revised edition (1981), since the text was significantly revised after new discoveries were made. For instance, the tablet was once believed to describe the resurrection of Inanna’s lover, Tammuz (also known as Dumuzi). Graves thus mistakenly lists Tammuz as one of his “Sixteen Crucified Saviors.” Of course, Graves cannot be discredited for this particular error, since in his day scholars still thought the tablet referred to that god (Kramer explains how this mistake happened).
There is great need of new work in this area. There really is a huge gap in modern scholarship here–this is one of the few subjects untouched by the post-WWII historiographical revolution. Most scholars today consider the subject dead, largely for all the wrong reasons. And there is little hope. The subject is stuck in the no-man’s-land between history and religious studies, whose methods and academic cultures are so radically different they can barely communicate with each other, much less cooperate on a common project like this.
So it’s as well to skip this book: it will fill your head with factoids of dubious reliability. Check out some of the more modern authors that Carrier mentions and go on from there. If you are looking for a PhD subject in an unworked field, perhaps reurrected saviors before Christ is for you.
…you will never be able to tell what he has right from what he has wrong without totally redoing all his research and beyond, which makes him utterly useless to historians as a source.