cpu and gpu are tied for #1. depending on the game, which is more important flip back and forth. so keeping them balanced will ensure you won't overkill either one to the detriment of the other.
in general cpu relates to fps more than the gpu. and the gpu relates to resolution and eye candy. balancing these 2 is essential so you get as minimal amount of one holding the other back as possible. one will ALWAYS hold the other back some, no way around it, but minimizing this is the idea when designing the system.