I can speak a little to this topic having coached a decade in both Indiana and Michigan. I like many of you may have played a game or two against teams from other states and watched film as well.
Here are a few quick observations.
Ohio: I believe is above the rest of the group by a sizeable margin. The difference in Ohio is the depth in my opinion, there are more teams of high caliber at each level, it's not top heavy or bottom heavy.
Kentucky: I believe is the bottom of this list. Population, and lack of a mega city anywhere play into this. Still many very good programs in Kentucky, but depth is lacking in all classes.
Illinois: the largest state by population, but also the most unique with the only true mega city among these states. Illinois boasts very few second tier sized cities lumping most of the larger schools, and most smaller private schools in one geographical region. Illinois has quality teams in each class, and posses a few Mega schools, but many of the mega schools (for whatever reason) are actually sub par compared to those a step down in size. The sheer size of the state gives it quite a bit of depth, but also quite a few poor programs.
Michigan: Michigan is unique because it posses no mega schools in the whole state, and only a handful in the 2,000's. For a state nearly twice the population of Indiana, Indiana's top 10 schools would all be top 2 or 3 in Michigan in size. What Michigan does have however are about twice as many football playing schools as Indiana. Michigan has 2 eight man divisions, and 3 11 man divisions all within the size range of Indiana's 1A. That's a lot of small school football. Michigan has a lot of depth in programs but the top really lacks "big programs" the way Illinois, Ohio, Indiana do. There are a lot of "kinda big schools" the smallest school in Michgan's biggest class is only roughly 500 kids bigger than the biggest school in the 3rd biggest class. Or another way of saying Michigan has about 200 schools that would be really big 4A, or 5A schools in Indiana.....that and in the small classes is where Michigan's strength lies.
Indiana: Indiana's real weakness is depth in classes, being a state with half the population of Michigan, Illinois, and Ohio that makes sense. Where Indiana's strength is at the top division with quite a good number of Mega schools, and the top end schools in each class tend to be quite comparable to other states. As we've seen the Indiana mega schools (and private school powers) can play with any midwestern states, it's after you get out of the top 5-10 in each class does the gap to the neighboring states start to win out. It's more a population thing than anything.
If I was ranking I'd say
1. Ohio
2. Illinois/Michigan
2a. Indiana
5. Kentucky
I know that's cheating but it really depends if you value depth over top end results.