Public opinion data and competing country rankings show no single, universally accepted answer to which country is “best.” Surveys from major research organizations find meaningful differences across populations and within countries, including direct disagreement about national greatness. The main caveat is that people often mean different things by “best.”
Caveats
Some supporting sources measure favorability or national pride, which are not identical to a direct comparison of which country is 'best.'
Part of the disagreement is definitional: people prioritize different criteria such as happiness, power, freedom, or living standards.
A few cited sources are weak or non-primary; the strongest support comes from established survey organizations, not commentary or secondary ranking sites.