No more useless than any other measuring system we have discussed. In fact this one is pretty straight forward, the number of tall buildings / people living in an area. Using the metro populations is a better estimate as was done for Metro Vancouver and Metro Toronto.
I am sure if Toronto came on top the tune would be a little different. Can't win ever stat.
This is no more silly (in fact a little less arbitrary) than # of meters of 150m, 100m, 80m, 35.6m, etc.. lists
Again, from the list above, at what height did you cut it off, 100 meters? 50 meters?? 12 stories (the common definition of a high rise)