Is gaming on Mac OS X possible?
I hate to disappoint you but I am afraid gaming on a mac is still very limited. 
Head to steampowered.com and see for your self. 

Although I believe that in the near future the major gaming publishers will see the opportunity with growing numbers of mac users and reconsider adding OS X as a platform for gaming.

Using a virtual machine is not recommended for gaming.
You can dual boot though and run Windows natively and games work fine this way. See Boot Camp