I have done so many weekend rides in this country that the roads have been fantastic, but the best road i have done is the Route Napoleon and a couple in Austria
There are so many roads that i would love to do, anything with bends bends and more bends
Chapman's Peak Drive out from Cape Town, South Africa. It's only short but in September / October you can see Southern right Whales breaching the Ocean surface, while you pootle along...but you've got to watch out for cheeky baboons running out in front of you.
One I really want to do is the Pacific West Coast Highway starting at Vancouver, with detours to see what's going on these days in the Mt St Helen's area in Washington state, some poking around where the settlers on the Oregon trail passed through the western rockies, and hanging out in Carmel just in case Clint Eastwood is taking the air......oooh and of course the Big Sur coastal route....sublime
Take the A68 east coast route south of Edinburgh any direction. There are plenty of blind crests and large dips.
The fun is to try not to back off as you approach the crests, it's difficult not to.