I have found a better one than the Great Ocean Road, which has been stuffed up for the first bit by ridiculous speed limits. I have ridden and driven on a large fraction of the roads in SE Australia, and this is the best I have ever ridden. I put it in the same class as the roads in Wester Ross in the Scottish Highlands.
It is the Channel Highway in Tasmania. I rode it last Sunday, and it was almost literally orgasmic. South out of Hobart on the Southern Outlet or Sandy Bay Rd, then onto the Channel Hwy at Kingston. The road follows the coast for 70 km to Cygnet with tight and sweeping bends, and fantastic views all the way. The road surface is generally good and there doesn't seem to be a lot of traffic. If you get stuck behind a campervan there are lots of places to pull over and enjoy the views while the road clears a bit.
Once I got to Cygnet I turned around and 3 km out of town turned left towards Nicholls Rivulet and Oyster Cove. The road through the hills is just as brilliant, with lush rainforest and fern gullies. You end up on the road south out of Hobart, about 30 km south of where you started.
If I had had time I would have just done it all again.
Karen.