A couple of years ago.. I did a "Great Lakes Lap"..
It was fun, because you can fly complete legs, real time.. with lots of scenery... And it IS a geographic accomplishment (though not on the order of globe circling).. and not as mundane, navigation-wise as like flying coast-to-coast.

Just treat all five lakes as one REALLY big lake; and hug the coast (including every peninsula an bay).
The FS9 scenery was interesting enough. The list of things you'll see is too long for this post..but Niagara Falls, Toronto, Isle Royale and the Mackinac Bridge top the list. There are dozens (if not a hundred or more) little airports to discover... Several Islands and a whole host of other neat things.