>>36368665Gen IV
Diamond and Pearl have a boring, shit story, bad Pokemon distribution, ugly Pokemon designs which ruin previous evolutionary lines, the Sinnoh is too big and annoying to backtrack through, and the routes have way too many bright colours and lack unique atmosphere, there are too many HMs, and they run slow as all fuck.
Platinum improves some of this but not all.
Also SoulSilver and HeartGold fix none of the issues present in their original games and instead introduce mostly inconsequential gimmicks like Pokemon following which are heralded as like the second coming of Christ.