I suppose it depends how you think of "hidden". In my mind, if you follow awards and gaming news, you're already in a fairly small niche of well-informed gamers. To people who don't stay on that pulse, marketing budgets and cultural moments can largely determine what's known or not known. Most of these didn't get much marketing, and few (like Undertale) had a cultural moment I was aware of. But I didn't include games like Hades which I love but kinda thought got a bit of both.
Ultimately, of course, you're right and I just took advantage of the question to list a bunch of my favorite games. 😂