Importance of CPU in high-end gaming
Once you reach the point where games start to require the best in video graphics like METRO 2033 or Crysis 2 whether because it is necessary for the complete visual experience or simply because it is poorly optimized, does CPU strength still play as big a role in smooth performance? I don't mean bottlenecking but for instance, would the performance from a GTX 580 and an i5-2500k versus a GTX 580 paired with an i7-980x really be roughly the same or minimally different?
It'll be the same. Once you have a cpu with enough power, the gpu becomes the limiting factor on your fps so in a sense is a bottleneck. But it really depends on the game, Metro is very gpu intensive and there are even games like AVP that could care less about cpu. http://www.tomshardware.com/reviews/sandy-bridge-core-i7-2600k-core-i5-2500k,2833-20.html
Then there are games like deus ex hr that the more cpu you give it, the more fps. http://www.tomshardware.com/reviews/deus-ex-human-revolution-performance-benchmark,3012-7.html
Games like metro and crysis are the common benchmark games because they require a lot of gpu power but still enough cpu power to get the full potential of the gpu. http://www.tomshardware.com/reviews/sandy-bridge-core-i7-2600k-core-i5-2500k,2833-18.html Once you get enough cpu power, the fps are the same.