The only games I've noticed that have a huge bottleneck on CPU was miraculously World of Tanks.
But it is understandable. From what I can tell, the code is CPU heavy because the majority of its userbase internationally are running on potato's.
Using my 7870 GHz Overclocked to mem and core clocks way higher than even the R9 270x, with my Phenom II X4 965 BE stock 3.4GHz. I get 29 to 45fps with sometimes 60 when I'm looking at static stuff.
But with the i5 4430 and the same GPU in my mini ITX summer rig, I get 45-60fps. Funny as hell.
There is barely any difference in other games though...real games that is.
There is a World of Tanks port for the Palm Pre/Touchpad and even the Blackberry Playbook.. Nuff said lol