Igadevil said:
I always figured Shadow Moon was more popular because he's the other Century King, he's Nobuhiko, he's an evil Rider, or just all of the above.
That's it, really. The entire lame (IMO) fascination with villains who just happen to share an outfit/powers with the heroes. This is what made people like those Ryuki asshats.
I liked Birugenia being a one-time contender for Century King -- if they had kept him around, there could have probably been some neater butting of heads with him and Shadow Moon, while he stayed on outside of Gorgom, and it would probably have helped Black shake things up a little in that second half. Hell, I'd even settle for Birugenia sending his own kaijin to go after Shadow Moon to wipe him out, so we'd have mini-Shadow Moon battle episodes.
If they wanted to hold off on Black's fight with him, they needed to do something more. But, again, the Nobuhiko actor not being used really, really hurt them. I'm sure we would have had some pretty cool dramatic scenes with Nobuhiko and his sister, girlfriend and Kotaro -- they just really needed to recast the part. Shadow Moon's voice actor, Masaki Terasoma, would have been pretty good, he's a well-trained stage actor (going off track here, I love those two episodes of Agito with him). Just think of the idea of Shadow Moon unhenshining...
Another thing I don't like about Black's second half -- they play "Blackhole Message" just too damn much! And that the Gorgom trio's "upgrades" made them look more like monsters of the week.