Granite Peak is definitely the best in WI - the only thing that sucks about GP is the 700000 feet of flats at the bottom of every run. GP is in the Wassau (sp?) area.
I always like riding Cascade "Mountain", too. Otherwise Devils Head isn't too bad. Tyrol Basin definitely has the best Park setup.
In Northern IL you've also got Chestnut "Mountain", which is pretty nice. About 20 minutes from there is a place called Sundown "Mountain" - they've got a good park setup - nice jump line and a pipe.
You'll be disappointed though in comparison to CO, obviously, but it's better than nothing at all. Gotta make the most with what you've got, ya know?