The soundtracks from 0 and 2 are my favorites, although it was really only the licensed tracks from Crazy Ken Band for 2 that I really dug. I'm so glad that those tracks remained intact with the US release.
I'm playing through Kiwami right now. I beat the Japanese version when it came out last year, and I was really just kinda "eh..." on it, despite the gameplay and engine being the identical to 0. I guess I never really liked the original Yakuza. I remember being so pumped for it when it was first being released on PS2 back in like, 2005. But when I played it, I thought the combat was terrible. The voice-acting was bad, despite having Hollywood "celebrities doing the dubbing, and the combat mechanics didn't get serviceable until Yakuza 2.
With Kiwami, all of that is fixed. I'm still not a fan of the story, but the new parts about Nishiki's story are great. My biggest gripe though, would have to be the cutscenes. The graphics are just as good as they were in 0, but the developers didn't bother to redo any of the cutscenes (aside from the ones that weren't in the original Yakuza). What you get are these fantastic character models with 2005 PS2 animation. I never thought that the animation in any of the Yakuza series' cutscenes were bad, but maaan...seeing the original animation now with these newer models just hurts and makes Kiwami seem like it was developed and released before 0 (which it kinda was, technically).
The Majima Everywhere System is fun, but it makes no Goddamn sense in relation to the narrative. I get it, Majima is an awesome character, and after being such a major part of Yakuza 0's story, it's understandable that the developers would want to include him more in Kiwami. But Christ, his impact as a character is incredibly diminished by having him pop up so randomly. Not to mention that his behavior in the cutscenes and his behavior in practically everything else (which wasn't part of the original Yakuza) almost contradicts each other. I always remembered Majima being more of an enemy than a friend to Kiryu in the original, although he wasn't a straight-up villain either. This was something that gradually evolved into the odd friendship seen between the two characters from Yakuza 2 and on. That's why they're relationship in the original was important, as this was the starting point for their growth. In Kiwami though, he's like Kiryu's best friend from the beginning. What a shame :-({|=
All that being said though, I'm really enjoying my playthrough of Kiwami much more this time than my first time. It's probably because I can understand everything now, but still, it feels like a wasted opportunity. Even for a "budget series" such as this.