This chart shows the relative performance of the top 100 cryptocurrencies by market capitalization as of June 18, 2017, against Bitcoin. Almost all of these coins ended with -99.9%
Bitcoin has proven that its liquidity, the trust of both small and institutional investors, and the network's unquestionable security are more important than the technical characteristics of its underlying layer. And of course, Bitcoin Cash, which some considered the "main competitor" to Bitcoin, has lost 99% of its value relative to BTC.
There are some coins that are technically better than Bitcoin and probably more secure than Bitcoin but here is the thing, Bitcoin was and is the best coin for massive adoption and that's why no other coin managed to beat Bitcoin. The reason it was the best option is that it was one of the first successful cryptocurrency and it's pseudo-anonymous, which means that it's not that big of a threat for governments because if Bitcoin was Monero, then it would definitely be banned before becoming massively popular.
Also, one of the biggest advantage of Bitcoin is that it's truly decentralized, we don't know who created it and we will probably never know it. There is too much money invested into businesses that involve Bitcoin and blockchain technologies. Every day, this coin just gets harder to beat.