You obviously don't keep up with the people here on Naruto Base believing that Hinata is underrated and Sakura is overrated.
My dear friend, you've got it all mixed up.
Due to the fans/bashers
Hinata: Overrated
Sakura: Underrated
And that's coming from a legit Sakura fan. .__.
Kind of depends on how you look at it, really.
Most people still think Sakura is the main heroine of the series. Whether she officially carries that title, or not - she doesn't fulfill it in anything more than a cameo. Zero meaningful character progression (even her "I'm a student of The Fifth" gets relatively stomped on when she's constantly the damsel in distress), a character that invites bashing ("Now that Sasuke is here - it's time for me to get serious and start being part of the team.... why are you all looking at me like that? Why didn't I do much to help Naruto before or open up a can of whoopass when we were all about to die? ... because my character whores out to Sasuke, that's why."), and has never once played a crucial part in the story's overall story arc (her -one- role is to cry over Sasuke leaving - which is completely unnecessary in the grand scheme of things).
In the roles where she -could- be a main character... we see Hinata brought in, or Neji, Gaara, Kakashi... Sakura is never to be found in the roles a main heroine should be in from time to time.
So, in that sense - Sakura's existence is over-rated, much more her character.
Sure - she has a lot of -potential-. But that's all it has ever been -potential yet unrealized-. Even now - she is being cast as the damsel in distress among the Team Seven group - while characters like Ino and Hinata as part of the Rookie Nine are doing just swimmingly with their teams. It's like Kishimoto has a mental block against making her character actually likable or deserving of complement.
It's frustrating, really - because she could be awesome as a main character without sacrificing the roles and intended purpose of other members of the Rookie Nine. But the ultimate litmus test for the role of a 'main character' would be: "What if x character had perished early in the series?" If the answer is "Nothing" - then they are 'extra' characters. If the answer is "a few scenes may have a little less drama or impact" - then they are 'side' or 'support' characters. If the answer is "the story we know would not be possible" - then they are main characters.
Sakura largely falls outside the function of a main character following the Chuunin exam arc - though it's quite possible that Naruto and Sasuke could have survived without Sakura in that instance. Her role in killing Sasori was largely arbitrary - another ninja could have been substituted and the engagement changed.
Hinata can be a little under-rated... but I'd actually argue that she's a bit over-rated in a number of instances. A lot of people would have rather seen her defeat Neji in the Chuunin exams than accept the atypical victory she actually enjoyed over him (she grew as a character by understanding that it was Neji who was suffering in the bickering, not necessarily her). Which is how Hinata's character tends to work. She embodies Yin more often than not - which means her victories tend to be somewhat submissive and passive in nature - but necessary and/or critical for achieving a longer-term change for the better.
Hinata could have beat-down Neji... but that would have just pissed him off at the head branch even more and not made the issue so apparent to Hiashi that Neji was prone to homicidal rage over the issue. Instead - she set him up for Naruto (and more or less pep-talked Naruto - which came back into play later). Thus began the
story's theme of choosing one's destiny, or how one goes about fulfilling destiny.