The creation engine might be built from the ground up, but looks more like a modified version of the engine used to create Oblivion, fallout, etc. New vegas was a glitchy, sad pile of crap made by obsidian. At least skyrim has a devout following of modders willing to fix every issue before bethesda does.
Skyrim, even when maxed still looks like a pixelated port, but is still a phenomenal game nonetheless