TL;DR:AMD's best current CPUs are the same speed (or slower than) their old Phenom II CPUs and run at the same speed as Intel's 3 year old CPUs.
Intel's newest CPUs are as much as 64% faster in Skyrim and, according to The Tech Report's article from August 23 2012 ("Inside the second: Gaming performance with today's CPUs"

provide much faster and more consistent framerates.
The single modern Intel CPU measured in this article costs $310 but you can get most of its speed benefit by going with the $200 i5-3470.