Guessed by @UnderwaterFunktown
The game that brought me back into the Pokémon franchise for a brief stint before it lost me for good a few years later. Black & White were the peak of this series' storytelling, arguably the only good games with a decent story to begin with - I got invested in a couple characters and the overarching plotline of this, and I can't help but wish the franchise had stayed on this path instead of... whatever happened after. Either way, I'll always cherish these.