If I'm being honest, I do not have any interest at all to move from where I am right now....my hometown in Indiana. I've lived several places and I'm fairly certain this is where I want to be. However, I love hearing others' answers to this question so I'll answer too.
I've disqualified any place I've lived previously...otherwise this post would be too easy: Asheville, North Carolina.
So I'd have to go with London. We were there in 2010 for a mini vacay and I loved loved loved loved loved it. So beautiful, a true world city. If money was no object, I'd buy a flat in Notting Hill or Bloomsbury and just live it up.
Another bonus is that you're pretty much a plane ride away from anywhere in the world.