You have to take into account what was available at the time that these OS were out. Windows 3.11 looks like crap when you look at it now. But back when it was out, it was looked at as high tech, wave of the future stuff.
So with this in mind, ME has to be the worst. It was a rush release and was so buggy that nearly everyone that owned it ran into problems right away.....
Pretty much my way of thinking. I fail to see how anyone could pick 95 either, OK it had its faults, but it was such a quantum leap forwards from 3.11, and it paved the way for 98SE, which had it been less liable to lock-ups and better at memory management, could have been the best ever version of Windows.