Well, maybe one more caveat: user expectations as they relate to the genre or company. One thing I noticed while browsing the hidden gems list* -- which have games with extremely high ratings -- is that there's a LOT of hidden object games on there. I think there's one cat series that appears like three or four times. And some more conventional genres like RTSes or action RPG's are hardly present at all.
I think this is due to expectations: people don't expect a lot out of a hidden object game, they're generally very simple, and a small indie title can easily meet those low expectations. Whereas a genre that has included many big budget titles, people have higher expectations, even larger, highly experienced dev teams have a hard time pleasing everyone.
But also, lists like that also implicitly often are euphemisms for “titles that are good, but cater to non-mainstream interests, and so never achieve vitality.” Hidden-object games get (probably unfairly and mostly self-perpetuatingly) classified as “girly games” — which leads to major game reviewers and journalists just completely ignoring them when they come out. So a good hidden-object game will almost always, inherently be a “hidden gem.”
Some games are so good that you may want to play them even if you're not the biggest fan of their genre. I guarantee you plenty of people played Undertale without being big JRPG fans.