voicerocker
Platinum Master
Charizard, Venasaur, Blastoise, Lugia and Ho-Oh say hi.
You forgot Pikachu!
All kidding aside, Charizard, Venasaur, Blastoise and Pikachu aren't Legendary Pokemon with an a storyline based on them. Gold and Silver were released before the concept of having the Legends made version-exclusive and were probably kept that way for HG/SS to keep that part of the games involving Lugia and Ho-oh intact. Though it could be possible to obtain both White Kyurem and Black Kyurem in both games, I doubt it because having them appear on 2 different games instead of 1 suggests they are version-exclusive.