Don't know about MOH, but your Q6600 at 3.0GHz is definitely bottlenecking the your GTX480. Ignore what CPU usage tells you...as it's not clear on pinpointing how the threads are spreaded across the cores...and I can tell you that Crysis DOES NOT really uses more than two cores, and your GPU usage being low also point to CPU bottleneck, as low frame rate during 99/100% GPU usage means the graphic card not keeping up, whereas low frame rate during not heavy GPU usage usually because of limitation on CPU's side.
If you refer to the following:
http://www.bit-tech.net/hardware/cpus/2010/03/03/overclocking-intel-core-i3-530/8
you can see that even the Q6600 at 3.7GHz is holding back the test graphic card (5870) comparing to the i5 750 at 4.15GHz, so for your Q6600 at 3.0GHz and GTX480, it would deliver lower frame rate than even the Q6600 at 3.7GHz with the 5870.
Either way, for a using a Q6600 with a GTX480, you should really ideally overclock the Q6600 to around 3.6GHz to remove...or reduce any potential bottleneck on CPU's side, provided that your motherboard is up to it. For games that are well-optimised for using Quad, your Q6600 at 3.0GHz most likely won't be much of a limitation for the GTX480, but unfortunately not all games are well-optimised for Quad...