Black & White
I recently replayed Black & White alongside a friend who had never finished it before. He got me to notice that the writing is very straightforward, and characters from scene to scene are basically spelling out what you're supposed to take away from it all. Even with that being the case, most characters are regularly making good points to consider. I think it's a great coming-of-age story, and Bianca in particular impressed me this time around when I paid more attention. Her arc is someone who really humbled herself, learned from those around her and was able to figure out how she could be of the best use to others when it really mattered. Cheren's character growth on display in B2W2 also shows a level of reconsidering what really matters.
I also think BW gets confused as being a message about pokemon liberation. It's not, it's a story about the perils of extremist views using that talking point as a vehicle. Pokemon liberation is supposed to sound enticing and like a solution to a problem, but the point of people brushing it off isn't saying "it's okay to own pokemon to use them to our advantage", it's saying the reality is pokemon bond with their trainers and are consenting, and the Plasma world view only works when you let fear dictate your choices instead of actually communicating. That's why all the characters grow when they meet other people and learn new perspectives.
I don't think there's another game that really delivers a message this well, but there are runner ups. Scarlet & Violet/Ultra Sun & Ultra Moon have some interesting characters and arcs, and the late game of each offer some of the most fascinating lore implications in the franchise. But they meander in a lot of places so the story doesn't feel evenly distributed. ORAS feels really solid and compelling to me, but I think I'm biased because I adore Hoenn.