Generally the scenic areas are close to lakes (including the Great Lakes) and rivers.
The Mississippi valley is deeper from the Illinois Palisades State Park and north. The SW corner of Wisconsin is hillier. Otherwise Illinois and Wisconsin are pretty flat.
Wisconsin Dells is a gorge stretch of the Wisconsin River, but very touristy. I like the Devils Lake area in the Bariboo Mtns better.
Door County is a peninsula with Lake Michigan on all sides. I like going all the way to Rock Island State Park. Otherwise it's hard to stay close to Lake Michigan on the Wisconsin side. I'm less familiar with the Michigan side of the Lake.
Northern Wisconsin and Minnesota have lots of lakes and woods. The Lake Superior shore is scenic, especially the NW part north of Duluth. The circle route around this Lake gets more remote.
State parks are a pretty good guide to the scenic parts of these states.