Female characters never got enough amount of justice in shonen genre itself and even Naruto isn't an exception, but that doesn't mean that liking the female characters from the Naruto is a really bad thing or something along the lines, although many people interpret it that way on this forum, typically. In the end, liking/disliking a character is just the matter of choice.
Sakura is a really poor developed character, I completely give you for that, but at the same time her simplicity is what attracts me.
Hinata was undisputedly heir of the prestigious Hyuuga, Kushina was the part of prestigious Uzumaki clan+ nine tails host, Tsunade was the granddaughter of first Hokage etc. Sakura, on the other hand, was one of the few 'simple kids', that achieved a lot in Naruto and that's why I prefer her over Hinata or others. That is obviously is my personal opinion and everyone is entitled to have one.
Avoiding character background unless needed doesn't really reflect the general portrayal of women being sexist. Especially since it's not just the women. We never learned about parents of Obito either. And he was important. Konohamaru's parents are absent. Minato's parentage or family is out of the picture. Nagato's parents were not named either despite being shown. Jiraiya and Oro didn't get a background for them before and beyond their days as a nin.
The problem in Naruto is that women enforces traditional gender roles and that doesn't go well with many because of the idea of working women. Women like Tsunade or Mei are typically unmarried. If married they are depicted as house wives. Women shouldn't have to lonely women to be strong or working women. Tenten works but her marital status is left out. One can only hope tht Kishi fixes the problem here in some random movie or chapter if she shows something contrary.
A manga which confirmed to general shonen rule and didn't let female characters overshadow male characters and yet managed to write strong character with dignity would be FMA.
And I like Hwa Rin from Ruler of the land despite her being used for fanservice. Because it is not excused by the manga verse and she hasn't declined with time.
The commercial toys side of Japanese fanservice is just...
I completely agree with your stand on Naruto manga and Kishi sucks at developing female characters. Even in the end, Sakura and Hinata, two lead(?) female characters ended up being housewives and nothing more than that.
As for others, they are just there to marry with other characters, there is not even a mention of what happened to their dreams(Temari, Tenten...etc).
One thing I would like to point here out is, every manga is different.
One Piece is an entirely different type of manga than Naruto, where Oda provides detailing of almost all the characters including Nami and Robin. So, if we are talking about development and stories of individual female characters, I would put Robin as one of the well-portrayed female characters in Shonen history(enies lobby arc is one of my personal favorites). Later, her development became rusty and as such, though I am expecting more from her as the entire 'void century' things get revealed(considering the fact that, current focus of the manga was something else).
Nami is oh well, Nami. She is a bit Lucy+ a bit of Orihime. She is a typical stereotype just like Scorps said.
I never really understood, why people liked Boa. She is typical Hinata type character and that's it, I guess. Though, she provides witty moments. Again, a matter of person choice here.
About sexualization, I rarely felt that women are sexualized in one piece, with few notable exceptions.(Rebecca, I mean what type of girl wears bikini while fighting against goons in Battle Coliseum?:|) Probably, because I take One Piece the similar way Scorps and other OP fans do and that's where Oda gains an advantage over Kishi.
About FMA, it did depict strong female characters, but one might argue that it is so because it is short manga and indeed FMA had that advantage. One Piece and Naruto, on the other hand, are really huge verses and typically when you handle such a big verses, you end up creating few stereotypes or what we call 'similar characters'.
Another manga, I would like to bring into discussion is 'Akame Ga Kiru'. It was a really impressive manga in the beginning, with few really good female characters, though it felt short of my expectations. Yet, I must say it was a different attempt in writing a manga with some good shades given to female characters, rather than them being 'glam dolls', which is an indication that things are changing.
