They may not manufacture the highest-performing cores, but they have consistently provided the best performance for the price. Who cares who's fastest? The consoles went with them because they were fast enough and better priced.
Need a citation on that.
For low thread count or FP heavy applications, i.e. the vast majority of cases, Intel's Pentium G series has been the best bang for the buck for several years now. AMD is only cost effective for applications with lots of threads doing integer work which isn't terribly common.
http://m.cpubenchmark.net/cpu_value_available.html
Low-end Xeons are on top, but the first you might want are the FX-6300 and 8320, followed by the Pentium Gs. Since you are not comparing equal cores, the cheaper Pentiums do make sense in a lot of cases, but AMD does often have cheaper motherboards. Actual performance is going to depend on use case. I feel like the console situation speaks for itself. AMD is still putting out some good stuff, especially for an undedog.
I still hope AMD will make another sudden leap like that, to keep the x86 market more competitive, but they seem more intent on keeping to the path started by Bulldozer...