I'd like a nice mix.
I want some areas to be dark, grim, epic, and moody... and others to be bright, jolly, and quaint.
This^
And I loved the fallout 3/NV world, oblivion was cool, but a little dry. Im excited for skyrim, cause they have learned a lot about map building from fallout 3, and a lot about cool features that make the game better(crafting,HC,ect) from NV. I think its going to be an amazing game.