Originally Posted by N3G4T1v3
They stated it is a new engine, not an enhanced existing engine. I feel the misconception is that they kept the same art style as FO3, even reusing some of the original resource (I'm sure they would have enhanced them), making it feel like the games engine hasn't "progressed" as much as expected.
TES3 through FO:NV used the Gamebryo engine.
With Skyrim, they created their own engine called the Creation Engine. FO4 is now using a modified Creation Engine. FO4 is only the second game to be made on this engine after Skyrim and considering the advances and modifications of this engine, I suppose that could be why they called it "new". For instance, 64-bit instead of 32-bit, etc.
Now another discussion can be had for whether or not Creation Engine is actually a new engine and not just a heavily modified Gamebryo. Edited by Sir Beregond - 11/2/15 at 8:57am