I grew up in Ontario near Lake Erie and went camping on the shore so many times as a kid and teenager. it was disgusting back then, but I hear it's gotten better. I always heard the American side, especially around Cleveland, was even worse.
Lake Erie is beautiful. The Great Lakes contain 20% of the worlds fresh water and you ain't getting it desert southwest.
Lake Superior is amazing, Lake Huron is very nice. I don't know anything about Lake Michigan....but Lake Ontario and especially Lake Erie were pretty gross in the 70s and 80s. I think they've done a lot to revitalize them the last few decades.