Bitcoin is Number 1 because as we all know Bitcoin is the 1st cryptocurrency to be introduced along with Blockchain. Being the 1st in the list it has its own Superior qualities over other coins in terms of its Value per coin, reliability, trustworthiness, longevity etc. As we know there are many other cryptocurrencies introduced in the market, some are trustworthy some are not, but Bitcoin is oldest cryptocurrency to ever enter the market and has survived till now and I think it will survive and will surely hold its Prime Position in the market for a longer period of time.