Best places to retire to.

My wife and I have been traveling to Europe for a few years now and are entertaining the idea of retiring here. We will have a sufficient income and our main extravagance is travel. Which countries have the best retirement visas and reasonable costs of living? Also important is ease of access to transportation be it air or rail. While the idea of Paris, Prague, Vienna, Budapest or the Amalfi Coast seems romantic, what would be a similar more realistic alternative? BTW we will be starting in Athens and ending in Rome in November and can't wait! Thank you in advance.