The best competitor to Ethereum is Bitcoin, obviously. I think of Bitcoin and Ethereum as the "Microsoft and Apple" of crypto. They are the biggest players right now and everyone else simply lags behind and doesn't matter. BTC is king because it has the first-mover advantage and it's technology is always improving (such as with lightning network) however ETH is currently used in ICOs and a big reason for the recent crypto boom, so give credit where it's due!