Ring of Kerry was nice, but also terrifying. The weather was also a bit of a downer the two times I've driven the Ring of Kerry.
I've never driven the Amalfi Coast Highway, although the wife and did put that on our list for a future anniversary.
As for the Great Ocean Road (and Amalfi, I'd guess), the big difference for me is the complete changes of scenery from the constant ocean views. With the ocean nearly always on one side of you, you can go from the California Redwoods further north, to the Golden Gate Bridge, the boardwalk of Santa Cruz, the mountains of Big Sur, lighthouses, sand dunes and grass plains in the central coast, to urban sprawl in the south with some of the best surf spots along the entire route. It's more than just spectacular ocaen views along a 550 mile strip. But I admit to being biased about the pacific.
