Nothing touches a heavily and properly modified Skyrim, just nothing. When you consider the world in which the game is played and how much can be achieved, its mind boggling.
If you gave me a couple choices modded and vanilla I'd go, in this order
1. Skyrim (modded with Realvision, ENB, with all the 4k texture packs, add ons etc)
2. Crysis 3
3. GTA IV (modded with ICenhancer, ENB, textrures, add ons etc)
4. Metro Last Light