The problem with the Ra example is that Ra isn't all three of those at once. God is always God the Father, God the Son, and God the Holy Spirit at once.
Hix, as much I as I also enjoy the OCRT, I know how to take it with a grain of salt. As they themselves state, they are religious reporters, not theologians themselves. They report what they find, and as a historian and who has taken comparitive religion courses before, they don't always have the best sources for their information. I know of that particular webpage, and they unfortunately don't give all the information correct, which is why its contense has actually changed repeatedly over time because they've been corrected many times about the facts. I myself know about the story of Horus, and to be honest, angels and many other things they suggest surrounded this god's life are absent. And don't get me started on Osiris or Krishna parallels to Jesus either.
The "truthbeknown" site is known to take whatever material that seems to make Christianity a conspiracy and use it, without checking for authenticity. I wouldn't allow my future students at public school to simply use anything they like, and I'm surprised you have here. The information given about Horus is inaccurate.
As for your last website, they've made a huge error. 1) they have no citations that I have seen, which makes me question it already, 2) they completely take many of the quotes of Early Church Fathers out of context (especially St. Justin Martyr's; that gave me a laugh), and 3) they obviously don't see that Christianity's theology on the Trinity, monotheism, etc, are actually different from the "supposed sources." Similar? No doubt about it, but still different. I gave a Trinity example earlier. Virgin Birth? It was God the Holy Spirit who overshadowed St. Mary and caused her to bear Jesus. Note that it wasn't God the Father, but God the Holy Spirit. And before you go right to the "divine-father-through-a-different-form," you need to ask if that form was a "Personhood" of that god, who could be that and its "normal" form at the same time. If not, there is no parallel.