Well the FX 8350 is faster than the i5 3570K in most things, but not really in gaming.
You can achieve the same performance with the AMD CPU, but in order to do that you must overclock.
This is a CPU test of Far Cry 3.http://www.techspot.com/review/615-far-cry-3-performance/page6.html
As you can see, the AMD provides significantly lower FPS then the i7, at low frequencies but in an enthusiast system, when both are overclocked to say 4.8 GHZ the results will be on par.
Far Cry 3 is a good example of a well optimised game, but all games are different.
For example in extremely optimised games such as Battlefield 3, the AMD will outperform the Intel, but in most cases it will always trail slightly behind.
And yes there's the power consumption question. If you're a dedicated gamer, the AMD is gonna cost you around 5-10 dolars extra compared to the Intel.