The history of Mew and Mewtwo.
Ah, look. It’s the reason I never could get into the first Pokemon movie.
Mewtwo is much more fun for me as a relatively simple escaped labcat than as a troubled evil mastermind who goes good in the end. There’s more for the imagination to run wild.
I think that’s what I like about games with sparse plots in general: whether I put it to pixels or not, I’m perpetually writing fanfic, and with the simpler plots there’s more room to run rampant. Filling in plotholes in silly game plots is a major pastime of mine, even or especially when it’s a game I love. Or, indeed, a stupid game in a series I otherwise love - meshing what’s salvagable with the rest of the series is kind of fun, even if I have to resort to “It was a fever dream” or similar. Sure, it means that other fans are going to have very different interpretations, but so what? That’s half the fun.
There is definitely a lot of room for more detailed plots in gaming (just see Pokemon Mystery Dungeon or Black and White, staying within the same series), but I like the simple plots, too.