See The Best Places to Retire Outside the U.S.
But if people really believe this and many of them go to a given country, things won't be very fun due to the crowds (which reminds me of something that Yogi Berra said about a restaurant: "nobody goes there anymore, it's too crowded").
This also illustrates what economist Steven Landsburg calls the "Indifference Principle." "Except when people have unusual tastes or unusual talents, all activities must be equally desirable."
This applies to any of the countries on the list in the article. Once everyone sees it as a good deal, they start going there. Only people with unusual tastes will really enjoy it. That is, you will have to like what that country has to offer alot more than the average person or the crowds and congestion will erode your enjoyment. That country won't be any better than anywhere else for retirement. Other places will be just as desirable.