Ethereum have a network of developers and projects supporting the Ethereum platform.
While other platforms have different and, arguably, better ways of handling certain parts of the stack, the truth is that 90% of developers and businesses building new blockchain applications are going to do it on the Ethereum platform.
This is a building effect. More developers means more projects, which leads to people making better Dev tools and learning materials, which creates better opportunities to create applications, which creates more developers and projects….
This platform effect is the most powerful thing going for Ethereum today. Even a killer platform that objectively is better than Ethereum on all fronts will have to overcome this network effect… which is no easy task.