BTC leads among all cryptocurrencies and ETH indeed follows second. You can check sites like cryptocoinrankings.com and coinmarketcap.com or any other site that is on the top when you use google. The industry of cryptocurrency is very dynamic and slight changes in the market reflects immediately in the rankings. So, before you invest on one or two of those, always check and analyze on your own if you need to change your strategy. Changes in ranking also of course reflects on the potential income you can get from investing.