There's some very exciting news today, with Unreal Engine now completely free, subject to a 5% cut of gross profits if your app makes over $3k. It's available for PC and Mac, with source available for Linux. This will be a serious challenge to Unity as the free version of Unity lacks some advanced features, especially lighting, whereas Unreal Engine is unrestricted. https://www.unrealengine.com/blog/ue4-is-free There's a guide here for current Unity developers, explaining how to migrate from Unity to Unreal Editor: https://docs.unrealengine.com/latest/INT/GettingStarted/FromUnity/index.html I'm 3 days in to development of a new iPhone game in Unity, but I'm going to experiment with UE tomorrow to see if it's worth switching. I dearly love Unity, it's a real joy to work with, but more and more I find myself writing complex shaders and scripts just to create visual effects that are built in to the engine but locked out of the free version. And I have no problem with Unity doing that, it's perfectly fair and I thank them for giving us the free version. But if a rival is going to offer a product as substantial as UE, feature-complete and free, then I'm certainly interested.