I actually looked at the numbers for some of these campuses, mostly in the west, because that is where I am. I was suprised to hear that people think that UA has the biggest greek system. I go to WSU and I know that we have one of the bigger Greek Systems in the West, so here are the numbers, and this includes IFC, PAN, NPCH:
Arizona State University - 39
University of Arizona - 44
University of Washington - 49
Washington State University - 51
Berkeley - 55
And just for kicks I looked up Penn State - 83
WOW!