In terms of price, BTC isn't actually the coin with the highest of value, there's 42 coin which is expensive than BTC. But btc however is much accepted by merchants and more popular than any other coins or tokens which I don't think there is any coin popular than BTC. I have talked to some BTC investor but they didn't know Ether. A chinese in the neighborhood doesn't even have any idea what NEO is.
Yes BTC is very popular and that would be a altkoin replaced it or caught up on the cost of what would have greatly increased the popularity of the coin and people would start to buy it and pay as BTC.