I\'m planning to write a 3D FPS game, based on WebGL.
There is a WebGL library focusing on web-game design and implementation called Babylon.js. http://www.babylonjs.com
Its strong advantage is that it provides lots of rendering effects in the library and you can just simply call these functions.
Of course, Three.js is a fundamental library for WebGL and all things are able to be implemented by it, just it may be time-consuming for game design. But I suggest you to start with Three.js to get familiar with WebGL and then use Babylon.js to do your game.