Epic's Unreal Engine 4 Rivalry project shows what's now possible on mobile devices.
Substance in Unreal Engine 4 Tutorial Series
Allegorithmic have created a tutorial series that covers how to use Substance with Unreal Engine 4.
Real-time Global Illumination with Enlighten and UE4
Epic Games and Geomerics created the video to highlight the latest physically-based lighting techniques in games.
Unreal Engine - Showcase
This compilation video shows off some of the games built wih Unreal Engine technology.