from my observation there seem to be a trend for which games this happens:
- very very hard games seem to go viral (e.g. dark souls, the worlds hardest game)
- horror games with jumpscares (e.g. fnaf, amnesia)
- multiplayer games (e.g. fall guys, recently helldivers 2)
- remakes of casual games that gone viral previously (e.g. flappy bird - before that helicopter game)
there are probably many more examples - pretty much anything that can be used for livestream content 🤔
overall it seems to me you need a different kind of skillset for making a viral game than just developing a good game
like there is more to it than just working hard .. seems beyond graphics and content too .. maybe it's just luck? 🤔
anyway I wouldn't be able to tell you what it is - I make the mistake that I make games that I want to play with
and in my games people usually get stuck on the tutorial level among other shenanigans 😓