See the Unreal 4 engine in action in this trailer for Primal Carnage Genesis.
Unreal + SpeedTree
Unreal Engine and SpeedTree allow for these beautiful outdoors shots to run in realtime.
Unreal Engine - Showcase
This compilation video shows off some of the games built wih Unreal Engine technology.
Super Mario Bros - Gulf of Mexico
Jonathan Fletcher has created an incredible reimagining of the famous Mario and Luigi video-game characters.