How about the 5 that are of most interest to you? Or how about the 5 that are of most interest to you within a reasonable distance of each other given how long you have to get around and visit them?

Your question as asked is pointless. The word 'best' is pointless unless you put it into context by providing sufficient background information. That includes, what are your interests, how much time do you have available, what kind of budget do you want to work with, etc.