All of you are just looking at Balance in a very simplistic dualistic fashion. George Lucas does not see this as balance. The idea that for there to be Balance there has to be equal numbers of Jedi and Sith is just silly- and that isn't what hapepns at the end anyway, as we are left with NO Sith, and the good guys Luke and Leia alive, so it is doubly silly. It really shows a lack of imagination to get stuck over this- or having read too much bad fantasy.
George Lucas made it clear that imbalance is evil. The Sith are evil, they bring imbalance. The Jedi are good, they bring Balance.
The Sith unbalance the Force. Anakin kills the Sith and therefore balance is restored. Therefore he is the Chosen One.
You could have a billion Jedi and no Sith and things would be balanced- in fact, they are much more likely to be, as that is what the Jedi do.
Simple as that- absolutely no more debate needed.
To answer the original question, no-one thinks Anakin is necessarily powerful because he will re-balance the Force. However, it is clear that the Chosen One is labelled in the Prophecy as being very powerful, because that is how Qui-Gon recognises him.
Meanwhile, the thing about it all being mis-read is because the Jedi never know. We know it was ultimately right because we have GL to tell us. But the people in the story do not, and they can doubt it.
The answer is given to us in ROTJ.