the kind of 'x-factor' is overclocking. a game really can't recommend someone overclock their cpu, even though so many PC gamers do
but I agree "quad core i7" is too vague. something like my old i7 860 would qualify, even though plenty of newer i5's would smoke that chip
there's also hyperthreading, but I've yet to see a game really use 8 cores like that (probably BF4). plus it's not magic, in that you're basically halving your clock speed to 'split' those cores. you're lucky if most games use more than two cores. although now both consoles do have 8 core amd chips, so we are seeing more multithreading
Ryse has that "Dual core with HyperThreading technology or quad core CPU (4+ logical processors)" requirement. I think that's good, because they're telling you what they need (4 threads). and some games do list a required/recommended clock speed as well
Wolfenstein TNO had the "Intel Core i7 or equivalent AMD" requirement, even though it ran great on my i5. that shyt is wack cause it's basically crying wolf, and now every time I see an i7 requirement I'm gonna think it's BS... and one day it might not be