It's hard to say, since there were several other stories of dying and rising gods which might have impacted the development of Christianity.
It is interesting that these legends were significant in the conversion of C. S. Lewis. He overheard someone remark that of all such stories, one of them seemed almost to have really happened (referring implicitly to the story of Jesus). This set Lewis to pondering the matter, and he concluded that it really did happen, exactly once. Thus Lewis became one of the most formidable Christian apologists who ever lived.
I think it is possible. Considering that Egypt had become agricultural 10 - 15,000 years ago, Osiris represents the cycles of the growing season. If you look at that in conjunction with Osiris being a metaphor for the vegetation and Jesus' body the wafer/bread, I believe Osiris could have inspired this. Memorize the prayers in the Book of the Dead so that when your heart is weighed on the scales of Ma'at, you will say the right thing and join Osiris in the reed fields for eternity. But as RLynn says, there are so many dying/rising gods that share this same concept, it is hard to pinpoint this all on Egypt.
Norse: Balder is the son of Odin, was born on Dec 25th and died by his brother's hand who was tricked by Loki. His wife went looking for him, just as Isis went looking for Osiris. When Nanna couldn't find Balder she threw herself on his pyre. Balder represented the light, and Nanna represented the vegetation. No light, no vegetation. This myth has always reminded me of Osiris/Isis and Persephone/Demeter all in one.
Celtic: Lugh was a warrior god of light, and was born on Dec 25th. He had a regenerative cauldron so that his followers would always have food to eat. (Lugh's town - London)
You could also find similarities with Seth killing his brother Osiris, and Osiris' son looking for vengeance... which was known to occur in most patriarchal societies...also to be found in MacBeth and Lion King
I've heard it said by at least one writer that the Christian story is anything but original.
You can throw in another god associated with the winter solstice: Mithras. He was very popular with the centurians, and the
main competitor to Jesus.
When I was in Egypt the tour guide was explaining the story of Osiris when we visited the temple of Isis at Philae. When he spoke of his ressurection he told us to forget everything when we left Egypt. I did not see the necessity in this display of drama: I think more people should learn of ancient religions. If Christianity is as strong as believers say, it should not matter.
On another note, there is a nongod that was a near contemporary of Jesus: Appolonius of Tyana. His story line is very close to that of Jesus', but somehow his cult did not survive. There are many factors to this, including marketing.
There are just too many similarities. When you consider the origins of the Christian faith, and the fact that a lot of what is known today was designed to make people comfortable in the transition from paganism to Christianity, it makes me wonder whether Christianity was literally just a transposition of the old time faiths. Osiris is Jesus, I'm sure of that-I just don't believe that either were a god.
It is amazing how many gods have a similar story. As for Christianity specifically, the Church was notorious for appropriating other gods (who were suddenly saints) and holidays. It was really a pretty smart strategy for converting people.
I believe the myth of Osiris and the story of Jesus Christ are strongly linked.Osiris[Greek form] = Asar [Ancient Egypt] =Ashtar/Athtar [Hesperus].
Osiris=Ixion [Aristaeus/Good Shepherd/Eunomus].Nephele = Isis.Centaurus/Chiron = Horus/Perseus/Mithras[Sun god].
Osiris = Vali [Norse] = Hades/Aidoneus= Busiris[killed by Heracles/Seth-Typhon].
Jerusalem was the city of Shalim [Hesperus].Shalim/Athtar also called Chemosh/Kamis/Kamus[god of Moab and Carchemish].