This piece from Basketball Prospectus is worth a look despite the caveats involved--they looked at attendance in the revenue sports in an effort to determine whether a given school is a "football school" or a "basketball school" or both.
These results rely heavily on two assumptions: 1) Programs design arenas and stadia according to realistic assessments of popular demand. (Though this is not always the case, particularly when college football teams play in NFL venues, but it is nonetheless something assumed true for most programs.) 2) Attendance figures reported to the NCAA are taken in good faith. (Again, one can point to many cases where figures are bloated, but with no way to control for this phenomenon the assumption will stand.)
The first assumption doesn't work for NC State (basketball), Georgetown, Seton Hall, Syracuse (basketball), Memphis (both) , Pittsburgh (football), UCLA (football), and South Florida (football), and probably some others. Still its an interesting snapshot of support based on percent capacity. Looking at the plot, you get a sense for how many schools cook their figures or are just fortunate to host opponents with big followings.
NC State falls just short of "two sport dominance" due to basketball attendance--the RBC Center has been about 70% full for Wolfpack games over the last six years. Considering the product on display in that time, though, I'd say 70% is pretty good. (Assuming the reported figures are accurate, of course.)