Why should Christianity be any more valid than let's say the Egyptians beliefs? Or Buddhists, Muslims (although I can make many arguments about the Qu'ran and it's contradictions) or any other beliefs?

Depends what you mean by "valid", I suppose. In some sense, I would say all religions are equally valid, that is that they have an equal right to exist and are equally meaningful to those who hold the beliefs. If someone wants to worship Ra, Buddha or Mohamed (or, for that matter, nothing), I would never stand in their way. In fact, I would do whatever I could to support their right to believe what they believe.

As I said earlier, I'm not a big fan of "religion", even the Christian religion. My faith is in Christ, not in the religion man built around Him. I think there is more good than bad in most of the world's religions, but I could never put my faith in something which is merely 'more good than bad'.

But as for why my faith is in Jesus as opposed to Ra, Buddha, or Mohammad, I believe that Jesus accomplished something that no one else ever has. I think that Jesus was the most extraordinary "man" (I use that term loosely when it comes to Him) that ever existed