Any games that utilizing a single core are likely old games that would benefit from overclocking if they weren't already able to put out 300fps anyway. I've been overclocked since the 90's and the last time I felt that overclocking had any impact was with my Q6600 C2Q, and only because it had ridiculous headroom. I was able to easily get 3200MHz out of a stock 2400MHz chip which is essentially 133% of the original clock, so a increase of 33%. Getting 400 - 500 MHz on a CPU that is already clocked at 3.9 GHz (turbo clock) just isn't worth the time, effort, cost (motherboard and cooling), for such a little almost non-existent return.
Most games are GPU dependent (except for RTS's, and high count multiplayer FPS like BF4), and the only way you can make the CPU bound is if you through a multi-GPU config that puts the bottleneck on the CPU.