The Greek Islands cruise was one of my favorites. I likes all of the islands and each had a different flavor. Rhodes has the Templar Hospital and old walled city. Mykonos has the windmills and is the party Island. Santorini, well it is just one of the most beautiful places on the planet with the White and blue buildings, the domes and the stone street.
For me it is Santotini, I remember sitting at a cafe with a view of the sea drinking the local beer and having Greek food for lunch, relaxing as the sun was setting. It is one of the places I would like to go back to and stay for a few days.