I'm not surprised by that answer coming from someone who doesn't know what Great means.
In all seriousness though, I voted Lake Superior. Lake Michigan and Lake Huron are really the same lake.
haha. You beat me to it. I was about to say that Michigan and Huron are just two lobes of one great lake, which is superior to Superior.
For me, Lake Superior, no doubt. I first sailed on Superior (shallow-draft markoni fractional rig), first fished on Superior (with hooks and worms!), and had some of my first non-pool swimming there (in late July, when the water is still very, very cold.) I've visited all of the great lakes, but only Superior holds superior childhood memories for me, so that's how I voted.