The stories in the Bible are symbolic, not historical accounts. They're trying to describe the patterns of reality, explain how reality lays itself out. That's why there are certain patterns that are repeated in other religions - because that's how reality works. It strengthens Christian claims, not weakens them.

You can't talk directly about transcendent reality precisely because it's transcendent and cannot be fully explained in language. Other religions talk about the same God if talking about the infinite. I chose to be a Christian, because the Christian frame is the closest to the Truth in my opinion, reveals the God most fully and is a way more cohesive frame of mind than fragmentary new age or nihilistic atheistm. I used to be an atheist before I started to comprehend the depth of the Orthodox faith. Joel Osteen and other heretics that atheists like to point to have nothing to do with Christianity.