I see where your coming at, somehow it's one of the series fun aspect, but it also somehow breaks immersion though, for me, really not that much. But I still think Bito deservs these red paintballs lol.
Also, I like how the hero sometimes becomes so angry that he destroys everything in his way. No such things in BK3 though, I guess he became wiser/acquired more self-control during those 4 years between 2 and 3.
But I'd admit the hero is what bugs me the most in these games. He sounds like a boy, but sometimes it's really difficult to imagine he's not a fully grown man. I mean OK, sometimes his reactions are over the top, but still.
I wish he had a defined name. I mean, the Zelda series has Link, the Ys series has Adol Christin, so it would feel more natural if the BK series' hero had a name. Especially since he actually talks, unlike some other action/rpg heroes.

I like three the best, and also like the breaking of the fourth wall and the fact that the game pokes fun at itself. That's not really about the story, though, so I don't think that has an impact.. the story itself is good because it shows how much the character has developed since the first game. I also think the voice should be a little different, I almost think multiple voices wouldn't be a bad idea, but that's me though. The fact that the story in BK 3 also has to do with teaming up with people and actually shows character relationships is one of the best parts of it. It's not an extraordinary work of fiction, but sometimes simple is best, as it ishere.

I also think BK3's story is my favourite, though I have to admit, when I played 1 and 2 with JGT, some things were quite difficult to understand, for me at least.
As for the hero's voice, maybe for BK1 and 2 it was fine, but considering BK3s story it's difficult to imagine why the hero would still sound like a boy.