From what I've dabbled in with the series previously, I believe they were generally "more of the same" up until the DS game that went unreleased in America which first introduced the character creation and stuff. I know there were some minor tweaks here and there throughout the series, but nothing as drastic as what they're doing these days. Character creation, choices in the story, completely separate stories, voice acting, casual mode, tag-team support mode stuff. It's all great and I'm glad they're starting to take risks, and be a lot more creative. I think how cookie-cutter it used to be was part of what turned me off back in the GBA days