Long story short, React has a much more graceful system of making the components generalized instead of the adhoc system that Ember and Backbone use.
Ember and Backbone have features that are similar to components, but components from two different sources will rarely work well, because often one component will break another. Anyone who has tried to put a bunch of different Backbone views from different people together has probably experienced this pain first hand.
React is designed from the ground up to allow components to work well together.
https://news.ycombinator.com/item?id=7738511
Long story short, React has a much more graceful system of making the components generalized instead of the adhoc system that Ember and Backbone use.
Ember and Backbone have features that are similar to components, but components from two different sources will rarely work well, because often one component will break another. Anyone who has tried to put a bunch of different Backbone views from different people together has probably experienced this pain first hand.
React is designed from the ground up to allow components to work well together.