Comparing apples to oranges. IPC wise the i5-4690k is going to wipe the floor with the older i7. It is still a powerful CPU, but in single threaded tasks it would probably lose out. On more generalized calculations the i7 would start to show some better numbers.
If you are limited to gaming only, the i5 is the superior choice. (Also the i5 has onboard video so it can game, if poorly, independently of a video card, whereas the 980x can't)
i7-4790k would perform nearly identical to the i5-4690k in games (i7 has 2mb more cache and hyperthreading) but would run a few modern titles a little faster because of the hyperthreading.
A gamer should get the i5 and invest the $100 savings into the GPU. If money isn't a factor the i7-4790k is the...