Years ago someone tried to argue against me on this issue that since the other Jinchuriki weren't brought up constantly like other stuff that Kishimoto would do, there was no "promise" that they would be as featured as Gaara.
And they got whipped by the Akatsuki to build the Akatsuki up. I don't know. I think it just makes those Jinchuriki look like losers more than it made the Akatsuki look badass.
Maybe they weren't constantly brought up or name dropped like other characters who finally got epic introductions, and Gaara was more to show what Naruto could have become and someone for him to relate to, but I still feel like we got ripped off.