Building a park of any decent "regional attraction" size, I think, is just not feasible. Just the cost of obtaining and preparing dozens (or hundreds) of acres of land; creating miles of plumbing, kitchens, bathrooms, infrastructure, pathways, employees... You've crossed millions of dollars before you've purchased a ride. And one might argue that you won't find a regional-draw amusement park that doesn't have at least one larger roller coaster, which can run $8 - $25 million dollars alone. Who's marching around these days with the hundreds of millions of dollars that it would likely take to bring a full-sized, regional amusement park to life, even in phases? And if they could, where would they build it?
Even Six Flags and Cedar Fair, whose main business is park operation, haven't built a park in decades. Acquisition was the name of the game, and that is over. There's nothing left to acquire, for the most part. The last attempt to build a park from scratch, as far as I can recall, was Hard Rock Park...
Another part of the equation, I think, is the expected scale of these projects. If Kings Island of 1972 opened in 2012... Suffice it to say, these are different expectations for a park in 2012 than there were 40 years earlier, for better or worse. Kings Island 1972 would cost millions and millions of 2012 dollars, but would even then would not meet the "requirements" that many have come to have.
That being said, I think that there is room for small, local parks like the one proposed here. It would be nice if Geauga Lake could be the family picnic grove with a few coasters, free from the expectation that it should have record-breaking rides. The problem is, who's willing to operate it? But I don't know. That's all just my opinion.