I'm going to exclude properties in luxury chains (Peninsula, Aman) from my answer because they are in my mind the answer to a different question, what is the best hotel group in the world?
I'm also going to answer twice, once for money-no-object and once for paying-the-rent.
@seville, we have very similar taste in cities and hotels. Cadiz and Seville, I could happily live there! I've not stayed in the Alfonso XIII but I have stayed in Los Reyes de Baeza, and I plotted to stay in the Monasterio Santa Maria but ended up in a dive in Cadiz for logistical reasons.
But you've missed out the best hotel in Spain and possibly the world:
Hotel Benazuza
http://www.elbullihotel.com
Fabulous super-luxury Spanish country house hotel (with 40ft high tiled ceiling bedrooms) run by El Bulli. The restaurant serves the Greatest Hits of El Bulli (rather than the latest inventions) but it is much easier to get into since guests get an automatic booking. And best of all, in summer (when no Spaniard would touch Andalucia and they all come to London for the charming rain), they have great offers (e.g. gastronomic weekend including the El Bulli 21-course tasting meal for 400Euros pp).
Also on the list has to be a Ryokan. I'm just not sure which one! I think because of meal they gave us (Ryokan is half-board: girlfriend had the kaiseki banquet, including octopus heads; I'm allergic to fish and got a Kobe beef steak, no questions asked!) and because it is in Kyoto, it has to be the Yoshida Sanso
http://www.japanican.com/hotels/Shis...32061&ryokan=1
Finally, closer to home: Combe House in Devon.
http://www.thishotel.co.uk/
It's a beautiful Elizabethan manor house with a great restaurant and the sort of natural, unstuffy devotion to guests that one normally has to go Asia or the better parts of Europe to find.
If you're feeling frugal, the list would be slightly different as the hotels start to win on the things money can't buy:
1) The restaurant with rooms Sa Carmen on Ibiza at Cala d'Hort. Every room has a stunning view of Es Vedra in the middle of the bay, you get to the beach long before the rest of the islands (and you can take the secret walk to the lost City of Atlantis) and you have one of the best paella joints on the island right beneath you. All for ~50 Euros a night.
2) The Cerulean Towers, Tokyo. A reasonably priced 4* hotel in trendy Shibuya and the best value-for-money hotel in Japan, in terms of service and, if you get a high corner room, for having a view of Mount Fuji from your bed and from your bath!
3) La Sablonnerie, Sark. Elizabeth Perre is unique, they don't make family hoteliers like that anymore. Sark is beautiful, especially in spring when the island is carpeted in wildflowers (so many bluebells everywhere, on the open grass, it appears blue from the sea!). The hotel is reasonable value (but not cheap, given it is a converted farmhouse) if you stay half board but, as the food at La Sablonnerie is excellent, it takes a lot to resist breakfast, lunch, tea and dinner in the hotel. If you don't, you will get fat while your wallet gets thin, as the extras charges will kill you. NB: Payment in cash or cheque only (may have modernised since)!