It's a matter of taste.
I just simply find Tasmania the most dazzling of all. I know other states and territories have their own beauty and natural wonders, but Tasmania won me over.
Of course, if I ever go to Australia, I'll try to explore as much as I can...especially Queenland (my grandfather spent most of his time there out in the bush and brought me good stories, kangaroo skins, and Aussie money), NSW, Northern Territory... Ehhhh I'll even try to check out all of the states/territories. You don't have that many compared to the USA.
Plus, Australia will be a good place for me to get used to driving on the wrong side of the road when most of the highways are out in the bush, countrysides, and outback. I'm just a little scared of learning in the middle of a UK city trying to focus on the traffic, get the manual stick right (I have basic skills of using it), and not accidentially go on the wrong side. I dunno how you do it when you rent a car in the USA. lol