Cedar Point gets that much attendance because it's a cheap alternative to Disney and Universal - for people in the North and Midwestern parts of the country, Cedar Point is more affordable than those two. However, you need only look at most Six Flags parks, DCA, Knotts from 1998-2010, 2011ish, DHS, and even IOA to some degree that appealing to thrill-seekers only bring hard-core fans, and definitely maintenance/security problems aplenty (gangs and teens would overflow the place)
Universal is desperately trying to stop being a thrill destination, and become the adventurous family destination. That's why all of the E-tickets for now on are going to mostly be family-friendly, along with smaller kids rides. They're trying to take on Disney, and 400 ft unthemed roller coasters won't do the trick. They already get enough flack from Disney fans that Hulk, Rockit, Dragon Challenge, and Doom are all poorly-themed thrill rides, which I can't argue with :look:
But no it wouldn't get 5-6 million in attendance - if that were true, the rumored Orlando Thrill Park would have gotten fasttracked
more like 2-2.5 million: a fringe park that might be a Six Flags-esque destination, but it would never approach the heights of the big parks. And Busch Gardens easily has some of the best coasters in FL, the best-themed thrill park in the state - 4 million in attendance. Think about that.