Each of the k12 pretty much showed that they matched or surpassed their parents abilities.
Ino, Choji and Shikamaru all surpassed their parents in their respective clans' secret jutsu.
Neji matched or surpassed his father and uncle.
Hinata matched them by completing the 64 palms and that rad lion fist dealy.
Kiba surpassed his mother by making the three headed super dog.
Shino surpassed his father with the giant bug jutsu.
Sakura surpassed or equaled Tsunade.
Naruto surpassed his father, and his sensei as Sasuke surpassed his father, Itachi and Shisui.
Lee will equal Guy, and Ten-Ten was able to wield the tools of the Six Paths himself!
So overall pretty good improvement.
There was also moral improvement.
The fact that Hashi and Madara were stronger then Naruto and Sasuke isn't that big of a deal because they grew up in a warring period where they fought constantly. Their power was in making war.
The important thing is that Hashi killed his best friend (who resurrected himself with Izanagi) and Naruto didn't kill his.
One created a cycle of violence the other healed it.