You could add Paxos to the Ionian list in view of the size of the island and the number of visitors, but when we were there we didn't notice foam parties, open air mega-discos or tattoo parlours. We were so disappointed!
On the other hand Corfu is bigger and has very up-market tourism as well as Kavos, which we once passed through in full swing! It's not just quantity of tourism, although that might be the case on Santorini.
Tony