After watching the brilliant documentary Gods Of Snooker Alex Higgins was certainly a one off great. Some may come close but these one offs can never ever be bettered. I think most on here have lived in an era of witnessing some truly brilliant geniuses in their sport which may never be repeated. Higgins in snooker, Botham in cricket. There are plenty more.
Snookers greatest shot
https://www.youtube.com/watch?v=xUH_JrxQBPs