Quote from Wikipedia >> The current release is Unreal Engine 3, designed for Microsoft's DirectX 9 (for Windows and Xbox 360), DirectX 10 (for Windows Vista) and DirectX 11 (for Windows 7, Windows RT and later); OpenGL (for OS X, Linux, PlayStation 3, Wii U, PlayStation Vita, iOS, Android); Stage 3D (for Adobe Flash Player 11 and later); and JavaScript/WebGL (for HTML5). <<

You are right that CryEngine doesn't use OpenGL it seems, but at least they are pretty close with PSGL and they also seem to be working on Linux support.