In spite of the protestations of many ignorant people, Christianity is quite a unique religion. Throughout history, mankind has invented many weird and wacky religions, but they all have one common theme: Worldliness. Christianity is unique in that, when you study it in depth, it lacks humanity's fingerprints.
The obvious case in point would be our central figure: The triune God. The Trinity is such a unique doctrine that even many pseudo-Christian cults reject it. It is fiercely mocked by unbelievers, and for good reason: It is far too glorious for us to understand. When God declared "my ways are higher than your ways, and my thoughts are higher than your thoughts", He wasn't lying.
But as difficult as the Trinity is to understand, it gets deeper, because the second person of the Godhead, the Son, actually became incarnate in human flesh. This is another thing that defies human religion. Man made religions are often based on pride. We often believe there is something truly special about us. We tend to make our gods our sock puppets, designed to give us some kind of worldly benefit. Once again, even Christianity gets hijacked in this manner. You have prosperity preachers, like Joel Osteen or Kenneth Copeland, who attract people by convincing them that God wants them to be rich beyond imagination.
In fact, when Jesus came, many of His followers followed Him for selfish motives. When they thought He would lead them to victory over the Romans and restore Israel, they followed Him as a conqueror. When they thought He would feed them endlessly, and heal their sickness, they followed Him as a provider. But the moment He stepped on their toes, telling them "you're sinners, be born again and receive eternal life", suddenly they weren't interested.
The fact is, man just doesn't make up gods like God. They don't make up sovereign gods who are impossible to understand. They don't make up authoritative gods who don't tickle their ears. They certainly don't make up gods who descend to our level and die in a manner we deserve so that we may be forgiven. But most of all, they don't make up gods that manifest themselves!
See, the most unique thing about Christianity is that our God showed up. No other god has done that. Even the founders of most of the world's religions (of course, excluding more recently invented religions) are dead. But the founder of Christianity is not only the very God we worship, but He also died and rose again!
So, we, as Christians, have a God that doesn't look like He was made up, and doesn't act like He was made up. The sensible conclusion is that He simply wasn't made up. All of mankind's silly gods are mere shadows of the real God. They are a testament to our natural need to relate to God, but lacking the reality to back it up. But that need was given to us for a reason, for while God is not in need of us, it is His desire that we relate to Him. It is for this reason that He walked among us, and even died the death we deserve. Only through confessing Him as Lord, and believing He rose from the dead, can we receive eternal life.