More cores being better for gaming is a misnomer. It's about having ENOUGH cores. If you have extra cores, they don't help, if you don't have enough, you'll have problems.
But you also need yours cores to be fast, the 7700k's cores are about 75% faster than the FX 8350s cores. You determine core speed between different CPUs by comparing their
=2874&cmp[]=1780] Single Thread ratings, not their clock speeds.(which only matters when you compare the same CPU at different clock speeds)
Because the 7700ks cores are so much faster, even though it technically has less, it's total score is still 30% higher. (The total score assumes the software uses all cores at 100%, only heavy video editing or benchmarking software ever does this...