Cocos2d-x and Cocos Creator vs Phaser.io

25% of iPhone games are made using Cocos2d-x.

This means you will not be alone in development, and will have access to a large community. You'll know you are developing for an engine that works.

Documentation includes a programming guide, API reference, video tutorials and massive reference test code project showing all functions and giving working code to the user.

A new feature since Cocos2d-x v3.1 is support for 3D models (in your 2D game), not only this but support for skeleton animations is included too! This awesome feature allows for impressive characters in your game along with easier, more fluid and realistic animations.

It supports Lua and Javascript with full feature support.
Especially with Cocos2d-JS you can develop games cross web and native, and the native solution have great performance with JS Bindings, much better than hybrid solution.

Cocos2d-x forums are active.

Cocos2d-x is not only open source but also supported by Chukong Technologies of China and USA.

Regularly updated and adding support for the latest technologies. 2014 has already seen the release of Version 3, a new Cocos Studio development toolkit (optional) and support for new technologies like skeleton animation systems Spine and Adobe DragonBone.

Cocos2d-x is C++ based engine and it has CPU advantages for most platforms because of that. It uses polygonal mesh methods for sprite rendering for using GPU advantages. (You also use quad methods for benefit CPU).

Because it is based on Pyglet.

On top of supporting pretty much all existing platforms (except consoles), Cocos Creator (Cocos's IDE) allows you to write 1 code that runs on Android, iOS, Windows, MacOS and HTML5 (not Linux though).

Through the use of SDKBox you can easily integrate 3rd party SDKs and plugins for each version of Cocos2D (Lua, C++ or JavaScript), you just choose the SDKs to integrate and SDKBox will do the rest.

For example, if you want to add a rating plugin, you use sdkbox::PluginReview::init(); and if you want to add the Vundle Ad Network SDK, you use the one packaged in SDKBox SDKBOX sdkbox::PluginVungle::init();.

It has a built-in Python interpreter that allows for easy debugging.

Cocos Creator (Cocos' IDE) comes with scene editing, UI editor, animations & particle editors and whatnot. It's also easy to use and pretty intuitive if you read the official documentation & tutorials. Way way better than the old CocoStudio.

Hundreds of video tutorials available.

You can choose WebGL or classic HTML canvas element for game rendering.

This is one of the most developed frameworks right now.

There are plenty of great learning resources available for Phaser.io.

Most tasks are done just using 2 or 3 lines of code.

If you're browsing Slant, you probably already have a JavaScript enabled browser, which is most of what you need to get started learning JavaScript. The requirement to run a server locally on your computer while developing might make things a little more difficult

All you need to do is attach Phaser script to a HTML page even without installing any extensions.

Phaser provides a similar approach as to that of Flash games, where you can load assets and place them on a stage, and even improves upon the shortcomings of actionscript. It is very easy to shift from flash to HTML5 development because of this approach.

You can use it in popular online editors like replit, codandbox, etc.

The creator of phaser(photonstorm) has given the older(Phaser 2.0) source code to the community for their own maintenance, and has made Phaser 3.0 with a different style and approach, trying to make it easier for beginners to learn.