How to address the subjectivity problem in hidden gems? Examples of underrated cases of high quality/ performance

I formulated my career’s mission as uncovering hidden gems and shedding light on them. Gems are highly valuable/interesting items. Hidden means that they’re not very well-known, obscure or underrated.

The problem I’m facing is that labelling an item as a hidden gem is quite subjective. The same item can be a hidden gem for me but quite unremarkable for someone else. I’m trying to make the endeavor more rigorous so I thought of the following cases to help guide my thinking:

• Posthumous success: Example?Herman Melville, author of Moby Dick and one of history’s greatest literary figured died without being known. In his lifetime, he was a hidden gem.
• Location/Environment: One becomes successful when they move to somewhere else. Example: Mo Salah’s mediocre performance at Chelsea before leaving to Roma then Liverpool. Chelsea’s Mo Salah was a hidden gem [A variation of this is where the item can be in two places at the same time — product that does well in one country but not another].
• Quantifiable metrics: Guess who the player with the best free-throw percentage in Basketball history? Nope, it neither MJ nor Steph Curry. It’s Elena Delle Donne. Now, obviously she’s quite famous in WNBA but when I heard about that, it was the first time I know of her; she was hidden from my perspective.
• Someone is looking for an item for a while and can’t find it even though it exists.
• Surprised Reactions like “I’m surprised I haven’t seen this before” “I can’t believe more people don’t know about this” “It fits like a glove!” etc…
• Writer’s writer or comedian’s comedian or Actor’s actor… Someone who is respected by the elite of the craft but not so well-known or successful to the average Jo.

Any tips on how to make this mission more rigorous? What would be helpful if you provide examples of hidden gems from your career and then we can take a stab on why it’s hidden.