Honestly, I blame the fandom for the fav. wanking. I blame Kishi too, but only because he's a gullible fool. But the fandom/ character bias within the franchise itself, end up trashing the series.
Sasuke was always first before Naruto. But that's only because you have Kishi who is an extreme Uchiha wanker, along with his assistants backed by a fandom who are also Uchiha apologists. We know enough about the Uchihas to actually create a college course about their history. Look at the arc we currently have. I love Sasuke, and I liked an ending where he traveled the world. But I hate the Uchihas, and the Sasuke wanking is unbelievable.
Then you have Hinata who is loved by otakus and self-inserts. For some reason they grew in size, and even more so when backed by SP, CC2, and Kishi's assistants. She was also okay with SNS before The Last. Sasuke might have gotten a jail-free ending, but Sasuke didn't have a good ending either. He abandoned his goals as well as Naruto; both being horrible fathers in the end. Plus SP hates Sasuke as well. Hinata, for a secondary character has gotten everything she wanted and more because no one in the franchise hates her, and you have a fandom that wanks her beyond belief.
At least Sasuke was part of the main cast. I hated the fact that Kishi was so focused on the Uchihas and Sasuke, and gave Naruto the short end of the stick. But when has Hinata made an impact on the manga? Yet, she had her own movie, had her own special filler episodes and most of her animation was made by her fanatics, and you have NNS that included scenes that were never in the manga at all, like her saving Naruto, and well as special move sets and being part of the main intro which hadn't happened, as far as I know in previous games. Hinata gain so much for some who wasn't even worthy as a secondary character (compared to characters like Shikamaru and Gaara).
SNS is also wankfest material, backed by majority, even though it's also crap.
In my opinion, Naruto grabbed the second to last of a short stick. This is horrible for a main character, but in the end Naruto was at a tug of war. It was Sasuke vs. Naruto, NS vs. NH vs. SNS, etc. and in the end one side was left being disappointed in the development. A lot of people sadly prefer Sasuke over Naruto, and some people saw Hinata as Naruto's number one choice, same with Sasuke. Some people see Naruto as happy with NH or NS or SNS, and some believe that Naruto should have died. With Naruto it's all up to interpretation of what they see is best for Naruto, even if it ignores canon. We can say that Naruto has the bad end of the stick, but others see differently.
Sakura on the other had never even received a stick, or her short stick dropped in a pile of mud. We had to find out about Sakura's parents in a semi-canon movie that not everyone would follow up in. We have to create our own backstory because we never received any. Sakura's only major arc was the Gaara rescue arc where we were introduced of her potential. She didn't even need to have a major fight again in the manga. But for some one who is supposed to be main female lead, she has very little. You have SP where most mistreated Sakura, and Kishi's assistants who could care less about her. Then you have a large hate base behind them. Since then, Sakura has been downgraded to secondary character, she has been mocked in some interviews, and then you have Gaiden. Sakura has more haters than supporters and most of her supporters now are pro-SS. Karin ended up being more mature in Gaiden. You have a lot of the fandom who are happy (NH mainly) that she's a secondary, and says that the role suits her more than main. You also have people who had hate strong enough to reach Kishi.
I just feel feel that the fandom, as well as bias in the workplace, had a lot to do with how each character will be in the end. This fandom is just toxic when it comes to favs. and hates.