1: who picks their holiday destination to impress other people
2: holidays arent always about rushing around to see as many tourist attractions as you can, sometimes people want to relax. and if relaxation is what you want, then adelaide is the go. none of this super fast paced atmosphere. you can take a tour of the wineries in the barossa valley (world quality wines). kangaroo island is a great place to relax, as is victor harbour.
if i was coming to aust for a lengthy period of time, i would take a week in the gold coast for the theme parks, a couple days each in melb and sydney then another week in SA to chill. even perth is a great place to chill out, and the swan river is pretty damn nice.
site seeing does not a perfect holiday make.