Sakura is the manga's heroine. She was the one present for the final arc and the one that helped bring Naruto and Sasuke home. From the way he speaks, Kishi considered switching due to popularity but didn't because he likes Sakura more.
Hinata has done nothing worth praising. If she's a heroine, it's in the anime. What Kishi has been saying lately about Hinata / NaruHina, it looks like he doesn't care if Hinata / NaruHina burn. Nothing he has said lately is good for Hinata / NaruHina. I hope the trend continues.
The best part is to watch the Hinata / NaruHina fandom scramble. There is no defending this, yet they insist. I've seen them compare Neji's death with Itachi and Jiraiya too. What the hell.