The original was just so cool it was unreal. The Mysterons were cool, the Angels were cool, Spectrum in general was cool, Captain Black was cool, and the plot was good, too.
The campy-ness of the Mysterons was so good because the way they operated made sense: Humanity was so underneath them technologically that they didn't need to use brute force, and so used wits and cleverness to out-manuever Earth's defenses and destroy it from within. One episode was a what-if scenario the Mysterons DID use brute force -- and the result were these UFOs that came and wiped out Spectrum like they were nothing.
Why??? Captain Scarlete was fine as it was just cut the booze and smoking
Brotherhood of the Bear Monkey Clonemaster , Anti Care Bears League,
Bureaucrat and BOFH of the HAB,
Skunk Works director of the Mecha Maniacs,
Black Mage,