Words like “best,” “top,” etc. usually indicate a subjective judgment. If something is the best, it’s usually just the best in someone’s opinion, not necessarily the most accurate, precise, etc. according to some objective measure. If no objective measure is given (e.g., if they don’t say something like “that sports star is the best in terms of points scored in one game”), I assume that it’s just someone’s opinion, and I suspect that they have some agenda behind calling it the best (e.g., they’re selling something).