Ethereum is not the fastest and most perfect system, and there are still many problems in their but ETH is a platform that is used the most. Beside that, in term of decentralized section, ETH is only second to Bitcoin and it's extremely hard to attack 51% into ETH system. In the other hands, their ecosystem is developed by the biggest community and be approved by many big investment funds. As a result, ETH almost cann't be replaced and beat beside Bitcoin.