I remember mentioning this once or twice on here, but unfortunately never got around to it.
There is a pretty mathematical and scientific approach for determining this.
QUESTION - Which country is the best?
HYPOTHESIS - Based upon all available data, accounting for the fact that "best" can widely different meanings and is defined by the person, the US is the best country.
EXPERIMENT - Collect data from any and all available sources. This data is to include any/all "top 10/20/100/xx" and similar lists, organized by country, on any subject matter that is relevant. The experimenter would have to interpret the list for "positive" and "negative" to correct for media or other bias. For instance, the top-rated country in a "Top 10 Countries in Income" list would be "positive". Conversely, the top-rated country in a "Top 10 Countries with Income Disparity" would be "negative". Invert all "negative" lists so that the top country is always the most desirable.
At first, I would be very reluctant to apply "proportional factors" to any lists. While it may be obvious that the list of "Top 10 Countries with Low Murder Rates" is a much more significant list than "Top 10 Countries for Cotton Candy", there is a lot of grey area in the middle where experimenter bias can skew the results. This might be able to be rectified if the experiment was done by a real scientist, with access to supercomputers, staff, grant money and time. The experimenter could attach weight to certain lists of significance by noting the frequency with which they are published, polled, linked in articles, and/or searched on the internet. A "Murder Rate" list is going to be run in papers across the country (world?), giving credence to its relative importance. A "Cotton Candy" list is going to be published and forgotten.
CONCLUSION - Collate all the lists and determine which country most consistently ranks near the top of all the lists. This country would be the "best".
My hypothesis is based upon a casual observation that, while the US rarely ranks at the absolute top of these lists, it's always near it. Other countries may rank high in a few (for instance, Uruguay may rank high in healthcare, but it's nowhere near the top in economic surveys). I call this my "Michael Jordan" test. Anytime that someone (usually Kobe Bryant) is called the "next Michael Jordan", it immediately says to me that he's not quite as good as Michael Jordan - otherwise, they'd be saying he's "better than Michael Jordan". In this situation, everyone is comparing themselves to the US, and in doing so, saying that the US is the benchmark which all others are measured against.
If anyone has some free time (and a few hundred thousand in grant money), feel free to conduct this experiment.