In Episode II - Attack of the Clones, there was a bunch of Jedi, like Anakin, Obi Wan, Yoda, Windu, Kit Fisto, and etc, while there was only 2 Sith: Count Dook and Palpatine.
The profecy said that Anakin would bring balance to the force. But, with more than a thousand of Jedi existing and only 2 Sith, the force wasn't actually balanced.
Then, in Episode III - Revenge of the Sith, Dooku dies, and Anakin team up with to Palpatine destroy almost every Jedi in the galaxy, and then, the only 2 Jedi left are Obi Wan and Yoda.
So, if we think about it, Anakin did bring balance to the force before Episode VI...