UDK is Unreal Engine 3 – the complete professional development framework. All the tools you need to create great games, advanced visualizations and detailed 3D simulations. The best tools in the industry are in your hands.
I rate this engine a 9, it is very good looking, well advance and perfect for making 2012 video games, I was going to rate it a ten but I have seen better looking engines like my ShadowEdge Physics Engine, the Game Engine used for Call of Duty: Black Ops (IW Engine) and the improved RAGE Engine used in Grand Theft Auto V.
To me, the Unreal Engine 3 is still great but has been around for awhile now and newer engines are being made and are surpassing the UE3 graphics.