At the moment Ethereum is I think fastest but I have also read about PolkaDot I never test it but the users say it is now the fastest blockchain. Actually, Ethereum has more load than others that's why some people compare it will low traffic blockchain.
How is ethereum blockchain be the fastest, it is not. I have made transaction with dash, ripple and digibyte before, there transactions are instantly or almost instantly unlike ether that will still take some minutes with high transaction fee. If not for the ethereum platform scalability issue, ethereum 2.0 will not be in process for launch.