I think Pokémon Go is doing pretty well at the moment - apparently it's got more active players now than it did during the hype around its launch. During the two years since they've added Pokémon up to Gen III (with Gen IV coming later this year), done legendary events, added Alola Pokémon, introduced friends and trading, improved the overall stability (though it's still pretty janky), and there are monthly community events. Oh, and it'll have interactivity with Let's Go Pikachu and Eevee (the Yellow remakes), that's almost certainly a factor. Also, the research quests give a lot more structure to the game, and Professor Willow's mythical hunts give you a sort of main quest to follow.