How do I improve gaming performance with Parallels Desktop for Mac?
Parallels will rarely be as fast as natively booting Windows via Bootcamp, especially when you're gaming. You're much better off ditching parallels and going back to bootcamp for gaming. By running the VM, you're limiting the amount of resources that are available to OS X and your VM environment; thereby, making each run slower. On some machines where a faster processor and large amounts of RAM are available, may speed it up, but it will never be as smooth as running it natively.