Recommending the obvious GOAT titles is getting kinda old now so I’ll go with my personal favourite genre right now: roguelikes.
In that genre, my favourite of all time are the Darkest Dungeon franchise, Slay the Spire, Loop Hero, Vampire Survivors and Dead Cells.
For me the biggest problem is not volume in general but volume of niche content. The best thing about Reddit was all the active, engaging communities that would sprawl around any niche subject you could imagine.