It's just the lighting and the blurryness. Nothing extraordinary in that video imo.
Well not entirely, but for the most part I agree with this. The shading, post rendering, texture quality and lighting of the Crysis engine is superior to what we've seen from Skyrim. The distant land and view distance (macro detail) is less impressive though and there's usually a bit less detail in the micro design. So there'll be less plants growing and less scattered rocks in comparison to Skyrim.
But as many have stated in this thread, graphics are only a way to get a certain atmosphere across. As long as there's an equal level in graphics across the entire game (so certain things don't stand out) and it's up to standards it's not something that makes or breaks a game. Especially not for games as vast as TES games. Skyrim is shaping up to look really good and may be even incredible on PC, but we haven't seen any of that so far.
As for mods making it look that good on micro levels? I doubt it. You'd have to rewrite entire parts of the rendering engine. You could get a long way in adjusting the lightning system and introducing new or better shaders and textures but in the end the engine is what it is.