You are right, though I think all three can be compared, depending on the type of project. Unity is on the decline and I would be happy for Godot to become the future for those types of games.
Three.js is a 3d graphics library, not a game engine. You can use it to render your game but it doesn't bring the same things as Unity or Babylon.
I have often worked directly with an html canvas and some javascript to make 2d web games. It works well for me and I enjoy it, but I wouldn't call it a "game engine" either.
The mobile builds are its killer app, in my view as a gamedev. Unity has lost the plot in many ways. Desktop builds are important too, but there's competition there if you consider browser/electron as a desktop platform, plus Unreal. But Godot is the exclusive up-and-coming competition in mobile builds (that I am aware of; granted I am not a mobile dev).
