I can no longer drink, due to a crook Liver. But I was not only a big wine aficionado, I've also worked in vineyards & wineries in SA's Clare Valley, which is famous for it's Rieslings. The winery I worked for was called Leasinghams, they made many award winning wines, with their Bin 7 Riesling a stand out.
The best reds come from the Coonawarra district of SA. This has a rich red soil, over a limestone base, near the coast, with exceptionally cold Winters & long hot Summers, which is perfect for reds.
Most of the swill, that goes straight to casks, comes from the Murray River, in Vic & SA. Though all regions make some contribution to that great lake.
Victoria & Tasmania make the best sparkling wines. & WA's Margaret River region also produces many fine wines, as does the Hunter in NSW (as Bo already mentioned)
There aren't many wines produced in Qld, mainly from Stanthorpe on the Granite Belt, where it's cold enough for grapes. They're not bad wines, but not in the same league as the southern drops.
Australia's most famous wine is Penfold's Grange Hermitage, which is a Barossa Valey Shiraz. It starts at around $600 per bottle, & can exceed $50K a bottle for the rare vintages!
I've never tried it, but would definitely do so given the chance. Bugger the Liver!
The rarest drop I've ever drunk was a 100 year old bottle of Port, which was unearthed during a clean out of a wine cellar at the winery I was at. Management put on a big feast for the workers, to celebrate our Riesling winning another gold medal, & they gave everyone a taste of the port, along with lashings of the award winning white. It was like liquid silk that a lit a fire in your soul. & that's another thing the Liver would have to cope with, should I ever be fortunate enough to run across a drop that rare.