Good franchises that fell off a cliff in the succeeding generation

[JCGamer55]

I want to say Kingdom Hearts because the series went downhill after KH2 (6th gen). I've heard Birth by Sleep was good (never played it), 358/2 Days was decent filler but then Re:coded was unnecesary filler (end of 7th gen) and everything after that is straight out mediocre (DDD and KH3).