I've always been very interested in these types of games. Grew up playing Neopets which was inspiration to becoming a software engineer. Am interested in gamified aspects as well. The thing I've not quite figured out is how to make these types of games _actually_ addictive? Neopets had a lot going for it IMO. Would love to know if this is actually working for you (and maybe others) personally and why.
I wish I knew why these games are so addictive, I collected Tamagotchi a few years back and ended up with a handful of originals and one of the fancy new color screen ones (that now goes for obscene amounts of money on ebay).