Paper Mario TTYD is a game that I can play the entirety of in my mind. From the very start of the game, I picture each area and recall the exact order of events from start to finish. Sure, I might not remember where every star piece is, or know the dialogue word for word, but I know the gist of it. This game is baked into me, like lights into a texture. (woah! sick gamer joke xd)
I love the worldbuilding. Taking the absurdity of the Mario canon, and giving voices and personality and depth to these weird assortments of Mario creatures. I mean, the center of Rogueport has a noose! And there are goombas just walking around, complaining about credit card fraud! Can you imagine that kind of thing in a modern Mario game? I've always loved worlds that clearly weren't meant to be that serious from the beginning -- Adventure Time, Homestuck, etc. but then as the story develops, these random silly elements are arranged in a way where there's actual depth and themes that weren't originally intended. And this game, I think this was my first time experiencing that kind of thing. A depressed bomb-omb laments the death of his wife, a toad seeks to uncover the murder of her brother, a big rat charges his expenses to the corporate credit card.
This game has such a strong heart. So much care and detail went into this game, and it feels like such a coherent, living world. Goombella will tell you the name of each character, and they'll all have a mini-story that develops over the course of the game. As someone whose favorite part of RPGs is talking to NPCs, I'm a sucker for this shit.
This game feels like one of the last of its kind made by Nintendo, where the world of the Mario Brothers feels fully alive. Super Paper Mario, Bowser's Inside Story -- these games carry on this soul. But Miyamoto refused to let this world live any longer. Toadsworth, Kammy Koopa, they've been killed off. Toads with individual names, individual stories, they were not allowed to exist. Each species must be uniform. There can be only one female toad, Toadette. No others. Stories sometimes steak into Mario games, But look at any of the new Paper Mario or Mario & Luigi games. They still have charm and fun, but they don't have an ensemble cast any more. The stories are serviceable and pleasant, but forgettable. Stories in Mario games are sequestered away -- you might stumble into Galaxy's library, and learn the humanity of Rosalina, but that's the exception.
Mario and Luigi, they can't grow or change. They are who they are, forever. But the side characters that these brothers met, they could. And I love Mario games, truly, and not every story needs a plot, and Mario platformers still have great soul without them. But there was something special here that it seems unlikely we'll see again from a Mario game.