IMDb votes (not to be confused with the other IMDb rating column)
I think it's the amount of votes each show has. So having a high rank just means a lot of people had an opinion whether good or bad.
I think the following link should have the same results. https://www.imdb.com/search/title/?title_type=tv_series&sort=num_votes%2Cdesc
Stargate Atlantis was cancelled, but at least they made it home. Those Stargate Universe people are in for a lifetime of torture.