One thing I know for sure about the Mediterranean, which is a place I go to a lot for holiday:
Either you go to local restaurants, or you go to really expensive restaurants. Avoid tourist area restaurants at all costs!
After landing in Malaga my wife and I went to this place called El Albero along the beach road, far outside the tourist haunts. For meagre 50 USD we drank three pints of beer each and shared the House Meat speciality, a 35 inch silver plate literally brimming with sausages, steak pieces, marinated beef and all sorts of delicacies and tapas. We also got rice and potatoes separately. For Spain that is incredibly cheap.
The next day we went to the tourist section and got a really small glass of beer each, plus a cracker with some prawns on it. This cost 50 USD as well, and the waiter nearly spat on us in the process, a truly rude and obnoxious fella.
Every place in Venice, Italy was the same, but I have a feeling we had lots of bad luck there. My wife visited the high end restaurants in Firenze, and she said it was heaven on earth. Same goes for the high end places in Rome (she travels a lot (business)).
Italy, France and Spain: The advice is the same everywhere: Ask the locals, avoid tourist restaurants like the bubonic plague.