We've just come back from 2 weeks in Spain. Did Barcelona, Valencia, Benahavis, Granada and Madrid.
I'd recommend all of them for their own reasons, but Valencia and Madrid are now two of my favourite European cities. Madrid is a sensational city, while Valencia also has the benefit of a great beach. Both have amazing architecture, great restaurants, excellent nightlife and cheap booze. Wine is cheaper than Coca-Cola in Valencia and I had a bucket of 5 Estrellas at a pavement cafe on the Gran Via in Madrid for 3 Euros last week while waiting for the Euro 2012 parade!
Take your pick - You can't go wrong with either of those.