The real problem with making blanket comparisons with the story of any number of Egyptian beliefs is that there are as many different interpretations of Egyptian mythology, it's causes, benefits, moral perspective, etc, as there are different rejected books of the new testament. The story of Horus and Osiris is just as varied from one city to the next as the story of Jesus varies from one text to the next. There are as many as a dozen different creation myths, involving several different creator gods, through out Egypt. The story of Jesus and his divine parentage and resurrection vary from one book to the next, as well. The difference is that one council was convened to agree upon the story that would best benefit the religion and the social implications that came from it being named the state religion. Ra, Ptah, Amon were all national creator gods at one point in time or another in the history of Egypt; it simply depended on which royal family came from which city at any given point. However, the question can be just as easily addressed by remembering that the bible didn't fall from the sky as an agreed upon and fully formed text. Men got together to pick and choose which parts and texts would best serve the mythology as it benefitted the religion they chose to force on people.
Christianity concerns itself primarily with the behavior of it's followers as those actions will ultimately effect what happens to them when they die. The Egyptian religion did exactly the same thing. The Egyptian mythology chose to claim that the divine was the creation of order, morals, justice and what can not be understood as the dividing line between "good" and "evil" and life and death. The Christian religion does basically the same thing. After Osiris died, he descended into the underworld where he served as the king of the dead and thusly also served as the paradise of order from the hell of chaos. This is why the dead Egyptian was judged in order to acheive admission into the kingdom of Osiris or if his soul would be cast into oblivion and true death, meaning the end of existence on all levels and in all forms. The Pharaoh served as the maintainer of order in the Egyptian world, Osiris served that purpose as King of the Dead in the afterlife. Horus was the son of that order, who every king identified himself with since at least the Middle Kingdom. Horus, Osiris, Ra; these are among the oldest gods in Egypt. Sometimes they're grandfather, father and son; other times they were great grandfather, father and son. But almost always Osiris serves as the kinggod, who chose to go and make order for the afterlife, so that the soul of the dead Egyptian had the option to live after dead in this life. But, being among the oldest of gods in Egypt, there is a lot of speculation if these gods were ever real men before being proclaimed gods.