The FX8350 is certainly good value, but it's cheap for a reason. Also, despite AMD CPUs always being cheaper and mostly better value than Intel CPUs, 75% of people have Intel CPUs, there's a reason for that too.
If the FX8350 is cheaper and better or equivalent performance (in every respect) to an I5, why doesn't everyone buy it instead of an I5 or I7? There's also a reason AMD are dropping out of the high-end CPU market, because they can't compete with Intel, no matter how cheap and good value they make their high end CPUs.
Regarding games using more cores, the problem is, the FX has 8 week cores vs the 4 strong cores of the I5.
The results below;
http://www.tomshardware.com/reviews/battlefield-4-graphics-card-performance,3634-10.html
clearly show, that an AMD optimised and sponsored game, which is designed to utilise 8 cores, still performs notably worse on a power hungry 125W 8-core AMD FX-8350 @ 4GHz, compared to a 2 generations old I5-2500k @ 3.3GHz, let-alone the more recent 3570k or 4570k, which only use 75W. In fact, the FX-8350 is closer to the performance of a previous generation dual core 55W I3-3220 than the I5. The current generation I3-4340 has 20% more performance than the previous I3, so it would likely match the 8-core FX-8350 in BF4, whilst still only consuming 55W and being $60 cheaper. Wouldn't this be better value?
There are also advantages of stronger single cores, not everything in windows utilises multiple cores, you don't want single threaded apps running slow, because the cores are weak.
I'm not saying the FX isn't good value, but there's a reason most people choose not to buy it and why Intel can charge more for their CPUs and still sell more.