It's all relative, imagine there's a game with 8bit graphics, but that stresses the cpu to the absolute limit,in that case the cpu will bottleneck most graphics cards, but right now, with most of the games out there, the minimum framerate is most likely to be determined by the gpu-this is why it is not worth it to buy a 4770k just for gaming, you will be better off buying an i5 and investing the difference into a graphics card.
There's no real way to compare a cpu and a graphics card with eachother, they do different things, but when a game demands x ammount of calculations from the gpu and y ammount of calculations from the cpu, the one that reaches the limit of the calculations required first bottlenecks the other.
/silly explanation