Recurring villains in the Sonic series

[RustyRick]

This came to mind last night, but somehow I can't help but think that the Sonic series is kind of lacking in the consistent antagonist department.  From what I can tell the only real villains that continue to always hinder Sonic and co. are Eggman and Metal Sonic. (Orbot and Cubot also count as antagonists, but they're used more as comic relief rather than seriously competent henchbots)  

Eggman Nega could also count as somewhat of a recurring villain, but he's really just a more twisted Eggman clone, so I can easily see why he's not used much.

And most of the other antagonistic type of characters often end up either becoming somewhat neutral characters in the long run like Shadow and Jet. The other type of true one-time villains out for destruction or world conquest are only relevant to one game only and either get sealed, killed off for real or in the rare case spared in the end, like Chaos, Biolizard, Black Doom, Mephiles, Erazor Djinn and King Arthur/Merlina. (Chaos and Merlina were the only ones who saw the error of their ways in the end so that was something if you ask me.)

What do you guys think about this matter? I would think that in all honesty Fang could make a nice return as a consistent antagonist who would only ally himself with the winning side, and thus doesn't become a real true likable character in any way in the eyes of the heroes.

[Spin Attaxx]