Sakura is meant to represent human weakness, and everyone is obsessed with wanting power in our world, to be strong and the best. Her weakness we all have but refuse to admit, so hating her gives us a feeling of superiority.
Others dislike her for fangirling over Sasuke, another thing almost every female her age and up does and is frowned upon in society for the excessiveness of it.
Most people (not all) like Hinata because she seems perfect and most girls want to be perfect or guys want a perfect girl, body and all, so they like her better.
If Sakura had acted like Hinata she would never be disliked, but she is the flaw we all do not wish to be.
This all just my opinion and what I've noticed.
Sakura is my fav because she is human, flaws and all and it's easy to learn from her mistakes.