What makes Steam so compelling for consumers is that it's more than just a digital storefront and launcher. They've expanded into so many different areas: Steam Input, Steam Remote Play, Steam Friends, Steam Workshop, Proton, Steam Marketplace, etc.

There is so much they do that it's not really just a store anymore -- it's an all-in-one platform. Most competitors do not come close to equal in any of these features; they usually just have basic launchers and maybe decent friend systems.

In my opinion, GOG is the best competitor yet because of their DRM-free installers and GOG Galaxy on windows which allowed you to have all your games in one place.