In Egyptian myth, Osiris was resurrected. Another god who died and was resurrected was the Babylonian Tammuz, who became a popular deity among the Semitic peoples, and most likely influenced the Syrian myth of Adonis, another god who died and was resurrected. The worship of Adonis spread to Greece, and today we usually think of him in connection with Greek mythology.
However, the myth most similar to Christian beliefs about Jesus is the legend of Mithra. Mithra was a Persian deity, the son of Ahura Mazda -- the Supreme Lord -- and the virgin Anihita. Mithra was born in a cave on 25 December, and was venerated by shepherds. He had twelve disciples, celebrated a last supper with them, died for the sins of mankind, and rose from the dead. He became the central figure of Mithraism, which also borrowed from other traditions.
Mithraism was a popular religion throughout the Roman Empire from the 1st century BCE to the 4th century CE. Its followers valued sexual propriety and self-control, celebrated Sunday as a holy day, practised baptism, and celebrated a memorial meal of bread and wine. The similarities between Mithraism and Christianity were so striking that Tertullian believed Mithraism was a counterfeit Christianity designed by the devil to lead people astray. Mithraism was finally outlawed -- along with all other non-Christian religions -- by the Christian emperor Theodosius at the end of the 4th century, but continued to survive for at least another century.
However, while it's interesting to note the parallels between Christianity and other myths, the mythical content of Christianity is one thing, and the existence of Jesus is another. If Christian myth isn't factual, that hardly proves that Jesus never existed. We know now that most of the popular legends about George Washington aren't factual, but we don't conclude that Washington never existed.