Really depends on what you play.
I had an 8350 at 4.7ghz, and an R9 290 when those came out. No kidding, the GPU would only run at 70% in many areas of BF3, BF4, and many other AAA titles at the time. If you play a lot of indie games, many of those aren't optimized well, and unusual bottlenecks with FX CPU's form because of that as well.
Anyways, got the 4790k the week it came out. Still have it at stock, and I instantly gained 10-20fps in most games, and my GPU runs at 99% every single title I own now. Why pay $650 for a 980ti when you just get the performance of a $310 970 out of it? Don't choke your hardware, get your money's worth. CPU/GPU balance is not a myth, most gamers overlook it.
It is a MUCH longer story than just that, let me assure you I have credibility. Replaced eery part in my PC, even the Mobo and 8350 itself, cleaned every driver install, tried every setting combo in the book, overclocked, underclocked, reinstalled windows more times than I could count. Hundreds of wasted hours, all just trying to see why performance was so hindered. Installed the 4790k, and in 1 hour, EVERYTHING ran perfect, just like that.
If just my 290 bottled, don't want to know how the 980ti would react to certain titles :/
Notice CPU's bottle more with lower resolutions, so unless you're gaming in ultrawide 1440p or 4k, don't stick with the AMD.
It's not a bad CPU, but very bad for pairing with 780/290 or better GPU. 280x and 960 have less issues since they're slower, and about the max the 8350 can handle (remember the 7970 was the fastest GPU out when the FX series was made, and AMD didn't plan ahead).