Well, opinions on food certainly differ, so I will drop my 2 cents and then let others chime in.
I have had good steaks at the Pilgrim River Steak House just outside of Houghton on the way to Chassell; The Library Restaurant and Brew Pub in downtown Houghton; The Michigan House in Calumet and the Eagle Harbor Inn in Eagle Harbor.
I am not a fan of fish, so I cannot refer you to a good all you can eat fish fry. Sorry!
Some other notable mentions are the ribs at the Loading Zone II in Lake Linden, the burgers and other sandwiches (as well as the view) at the Bear Belly Bar and Grill in Lac La Belle and authentic Mexican at Carmilitas in Calumet. Just about any place open for breakfast up here serves a winner too! Almost forgot. It's pretty hard for me to pass through Twin Lakes and not stop and get some bacon cheese fries at the Parkview.
Hopefully others will give their favorites.
Enjoy your time here!
-John