I have not invested in crypto currency yet. Late to the party. I'm considering it.

I'm wondering about the inherent value. I get that it's better than fiat currency in so many ways. Best is the peer-to-peer over-coming the lack of trust thing, and for no fee. It's good currency. I get that. I agree. My question is why any one currency over another. So I thought this thread was the best place for this.

Bitcoin is the established king. But what is to stop someone from copying it? No, really copying it. As I understand it, all the altcoins are different in some way, usually trying to improve or be better than the other altcoins. But, why not make an exact copy of Bitcoin? Why not 500 copies of Bitcoin? Why not 500 copies of Ethereum, Neo, vert, etc.?

tldr: I accept that cryptocurrency is a valuable thing, but I don't see how it holds its value against other cryptocurrencies. What am I missing?