I was thinking of Costa Navarino too but you'd need to hire a car to get around and to the nearest town (which is about a 5-10 min drive away). There are two (interconnecting) hotels there and Los Romanos is better (and more expensive) then the Westin. The food is good, maybe not great. It's a stunningly beautiful area so worth exploring. There are also loads of super-stylish resorts on Crete - although the only one I've stayed at is the Amirandes near Heraklion (which was nicer and had way better food than the Costa Navarino, although the surrounding area isn't as beautiful). There are a whole bunch of super-luxurious ones at the Eastern end of the island, around Elounda.
A few people I know swear by the Forte Village Resort in Sardinia, but I haven't been there myself.