There's no right answer here. You'll get responses like "India" or "Costa Rica" which have expat populations - but also have to be okay with spending 4k on plane tickets whenever you want to visit the US for a grandkids' event. And never do things like see a Broadway show if that's your jam.

"Best" is going to be a value assessment based on a host of factors like access to your children, access to specific recreation, and so on.

So what do you value?