Most games aren't very CPU intensive since the stuff that runs on the CPU generally isn't scalable (essential gameplay and logic), and their minimum requirements need to be fairly low.

Point being, animation is by default performed on your CPU, and animated vertex counts will have a direct effect on your performance, and your CPU probably isn't very fast (even if your PC can handle beastly games).

Use a bones-animation shader to move animation onto the GPU. Look up matBones in the manual.

Jibb