Ethereum is one altcoin that has a large community and many other altcoin project are still working under the Ethereum today. BNB and DOT are competitors and no one know what the future of these altcoin will be like. But I still firmly believe those two altcoin won't kill Ethereum for a long time, but it could still happen if Ethereum fail to fix the fee problem.
There have been many who have tried to compete with the ethereum platform, but many of them have not succeeded because the ethereum platform has been used by thousands of alcoint which are currently circulating on various exchange markets and there are many more alcoint projects that are being built using the ethereum platform ... maybe it could surpass ethereum but not for the resilience and popularity of the ethereum platform which nowadays every cryptocurency user must have.
All the altcoin on the market today especially the top 10 altcoin are Ethereum's competitors to be the best. Although someday there will be altcoin that can beat ethereum's current market capitalization, but in term of usability, I think Ethereum is still superior.