Question: What makes the story of Jesus’ resurrection different from other pagan resurrection stories, such as those surrounding the Egyptian god Osiris?
Answer: In Lord or Legend? (and more academically, The Jesus Legend), Paul Eddy and I address this, and many other, objections to faith in Jesus. I encourage you to check either of these books out. But basically, if one examines the details of the various mythic accounts of dying and rising gods, there really aren’t many impressive parallels to the Gospel accounts.
For example, consider the example you yourself give. As the story goes (at least according to one of the versions that’s come down to us) Osiris was killed by his brother, chopped up into fourteen pieces and scattered throughout Egypt. Isis then rescued all but one of his body parts, reassembled them and brought him back to life. He was then given rulership of the underworld (the realm of the dead). To claim that this account “parallels” the Jesus story is quite a stretch, to say the least. Indeed, it’s not even clear we should call it a resurrection account since Osiris was never fully reconstituted. Not only this, but poor Osiris really wasn’t brought back to “life” at all since his resuscitated rulership remained in the realm of the dead!
If you examine all the alleged parallels to the Jesus story, this is pretty much what you find. Like they say, “the devil is in the details.”
Having said this, I want grant that there are vague parallels to the Jesus story in pagan myths throughout history and around the globe. But far from concluding that these vague parallels in any way discount the historicity of the Jesus story, Paul and I argue that they actually confirm it. If the Jesus story is in fact true, we should expect parallels like this to exist. After all, one aspect of the Jesus story, extending back into the Old Testament, is the teaching that humans are made in the image of God (Gen. 1:26-28). We’re thus “wired” for God, if you will. Not only this, but the New Testament itself declares that Jesus is the light “of all people” (John 1:4, 9) who is always working in the hearts of all people to lead them back to himself (Acts 17:26-28, cf. Rom 1:19-20). We should thus expect to find “echoes” of the Jesus story expressed in the myths and legends of all people.