I can't see how anyone can say that western games have good stories and characters with a straight face. Of course there are rare gems like the fallout games or PST, but if you want a good story and characters, go and grab classic novel.
I think that both types of games are generic in their own way in terms of story. Being a westerner however makes eastern cliches less generic for me. Not to mention gameplay.
Also I can see how one can dislike a jrpgs combat, but apart from bg/iwd, fallout and toee there wasn't a single western rpg which's combat I enjoyed since crawlers like MM.
Anyway, regarding the question... I think the answer lies in the recipe they use for their games. Gameplay still hasn't changed much since the earlier games, and while retaining some elements they inherited from old crawlers, like optional harder content, maybe even the base setting of mixing sci-fi and fantasy, they always had their focus on the more 'artistic' side of desiging, like the setting itself, concept art, environments, music. Add to that their opportunities at art design really increased as 3d came in. Also, as a result they tend to experiment more with alternate settings, just take a look at valkyrie profile, or other long-running series like megaten.
Western RPG's on the other hand lost their focus on art design and settings, probably as a result of rpgs losing popularity, because mainstream customers didn't really dig western style weird settings. As an example remember how customers were spamming 3DO to remove the Forge from Homm3's first expansion. For anyone who played the rpg series (the fans of the series) the Forge made sense, since it showed the consequence of the player's choice in MM7. Yet the publisher/dev chose the mainstream instead of their fans, and it has been like that ever since for most companies unfortinately. Then they started to release crap on every existing platform till they disappeared. Good riddance.
