>>57360899For me it's the urban fantasy setting full of a wide variety of creatures that are dangerous but entirely possible to befriend, mysteries to solve/lore to discover, and the freedom to do or be whatever you want. The concept works a lot better as an anime or ttrpg than as any one single video game can present, but when you look at the games collectively they come pretty close to filling the concept's potential.
Hey You Pikachu and Channel give you a look into the domestic experience of living in the pokemon world. Stadium and Battle Revolution are pure competitive with mini-games in the former and a theme park setting in the latter giving them the big event with something for everyone feel like a county fair or the olympics. Mystery Dungeon and Pokepark are slightly different settings where the humans are gone and the pokemon themselves are running things, but it still works as a glimpse into what wild pokemon society is like since they're generally more intelligent than real world animals. The main series tries to provide a little slice of everything but focuses on the catching and training, however due to them being tied down to handheld consoles they've always been technically limited in how much they could have in them even if Game Freak were competent devs.
Even if they did go for releasing on the more powerful home consoles there'd still be limits to what they could do given the time and budget constraints and better hardware still isn't unlimited power. Even if they moved to pc where they could keep expanding one game indefinitely as hardware gets better instead of starting over every few years and dropping features to focus on new ones, the reality is a video game will always have a limited scope compared to the whole world it's trying to portray. There will always be stuff to add, stuff getting overlooked, stuff that sounds great but would be impossible to implement right, and boundaries you can't explore beyond.