I was gutted, meant to do Santorini last summer but I was late getting over to Crete and the missus had to go alone for a couple of days. She loved it. Been to Kefalonia, beautiful part of the Ioanian but Corfu is my preference. Especially up north, Sidari is good for families but that stretch of coast from Acharavi, through Kassiopi, Kaloura etc is beautiful and really quint Greece. I also like Paleokastritsa there.
Halkidiki is good on the east coast, depends what you're after. The bottom peninsula of Kassandra is more touristy but still very sleepy. Because its on the mainland you'll find that the accommodation is better than most of Greece. Sithonia is the middle peninsula and very quiet, nice place.
Thassos is stunning, I'm desperate to go back there mate. I liked Mykonos but it's for a livelier holiday.
Never done Rhodes but heard loads of good stuff about Lindos, got a mate living over there so may do it some time.
I prefer the smaller quaint parts of Greece, like the tiny islands but I can't say I know them that well. Reidy is your man for that, he lived out there and knows some boss wee places.
It's my favourite part of this planet though, beautiful country and amazing people. I'm going to my Greek friend's place on Sunday for Easter, which is massive in Greece, bigger than Christmas. Can't wait.
mate did corfu last year, raved about it, lindos is right next door to pefkos, like chalk and cheese but its a lot cheaper in pefkos more family, going to google those places you have put, but you nailed it on the head the people are brill, have a great time sunday believe its really good.