I agree, however brilliant Skyrim is, the Witcher 2 is better in every aspect except the freedom that character creation and the open world offers in Skyrim.
In terms of graphics, story, gameplay, characters the Witcher 2 comes out on top. Having said that, I am not denying that Skyrim is an excellent game, but the Witcher 2 shows how to do things: develop for PC first, then scale back to consoles.
The Witcher 2 hasnt been released on consoles. Also, in my opinion, it makes sense to start with the static platform for development that is the (outdated) 360, rather than develop for the moving target that is the pc, and scale back to the console.
The reason the Witcher 2 is a better game in many respects than skyrim has nothing to do with graphics or being developed on a pc. Its to do with the better writing of the development team.