The real answer's a lot more difficult here, as there's no hard-and-fast measure.
Simply put, it's 100% application specific; each game can place a different load on each machine's parts. Some games are much heavier on the GPU than the CPU, and others vice-versa. So it'd be useful to know what applications (games) you'd like to run are.
While it's often-repeated truth that the Core i5s offer much better gaming performance than AMD FX CPUs, citing that as an answer is shortsighted twofold: for one, the asker may already have an AMD motherboard, so once you throw in the cost of a brand-new Intel motherboard, the benefit may not be worth the purchase price. Secondly, the benefit may not be that great at all, depending upon the application in question. And of course, the SETTINGS also place a huge impact, too: it's very easy to crank settings up and down to adjust the load on the GPU... But not so much can be done to impact the load on the CPU in most cases.
As a couple of examples, at the extreme GPU-heavy end, we have things like ARMA 3: If you're enjoying it on its mouth-watering Ultra settings, your CPU largely doesn't really matter: your "mere" 290X is liable to be dragged down unless you've cut the resolution a good deal.
At the opposite end are games like Battlefield 4, or especially a lot of strategy games: your CPU can make a FAR bigger difference in those. Or to speak of an older game... Skyrim, for instance, if heavily modded, can present a load almost entirely on the CPU; by now video cards that are positively ancient could handle it fine, but even a decent CPU could get bogged down.
Long story short, it hinges on what you want to play. Adjusting your graphics settings, it's actually possible to get a balanced load with just about any reasonable CPU and your video card. It's just a matter of making it so that balance is a place you're happy with. Chances are, however, that even a less-expensive Vishera chip like, say, the FX-8320, will get plenty enough playable performance in modern games. If you feel like you'd want to bump it a little more, go for a FX-8350. Neither will reach a higher-end i5, but you're not going to be able to reach that level. Fortunately, things should still be plenty playable nonetheless.
Facebook
Twitter
Instagram