Is retiring overseas really for you? I'd say the very fact that you're even considering the notion of retiring to another country gives you part of the answer to that question. Because considering the idea means you possess one of the two qualities you need to make a big success of this: open-mindedness.
Before you spend a lot of time and money conceiving a plan for a new life overseas, take a close look at the options for establishing residency in each country on your list. Understanding the various visa options available to you is an important part of making your ultimate where-to-retire-overseas decision.