FWIW: U. S. News & World Report (bless its heart) has prepared listings of schools with the highest percentage of students in fraternities and in sororities (but apparently not of total Greek, male and female). Aside from the one ranked first, which is obviously a special case, these seem to be interesting and not especially surprising lists. Are the lists totally accurate? Hey, probably not. Are they fairly accurate? Probably, within reason and subject to expected reporting errors and glitches.
Fraternities (22% and higher)
http://colleges.usnews.rankingsandre...frat_brief.php
Sororities (25% and higher):
http://colleges.usnews.rankingsandre...orit_brief.php
The lists
don't say anything directly about Greek system "strength" at schools. However, they may spur some thoughts on the topic, or at least remind us of colleges and universities that we didn't have at the forefront of our thinking.