It would help if there was:
A/Some marketing
B/Some regularity
About a Rabbitohs and Roosters game early in the season.
A/Some marketing
The Broncos vs Cowboys is being dubbed the "XXXX Derby."
The Dolphins vs the Broncos is being nicknamed the "Battle of Brisbane."
There was plenty of online advertising for the Waratahs vs the Brumbies, and a big push to get the crowds through the turnstiles.
Heck even the A-League puts a bit of effort into branding Sydney FC vs WSW (Sydney Derby) and Sydney FC vs Melbourne Victory (Big Blue).
A regular season Rabbitohs/Roosters game generally just coasts along without any particular focus from the NRL marketing team (or the marketing teams at either club for that matter).
B/Some regularity
Whilst it's common for the Rabbitohs and Roosters to play each other early in the season, and then in the last round of the year, it would be good if they got a prime slot to maximise crowds on a regular basis (given, even without marketing, it is THE regular club game in Sydney that can pull a non-public holiday crowd). 8:00pm Friday night or 4:00pm Sunday afternoon should be a regular thing.
It would also help if both clubs based themselves out of Allianz Stadium and the rivalry also became about being the "chief tenant," but that's on hold until the NSW Government sees the light and tries to play its minor role in fostering the rivalry and allows them both to be based out of Moore Park.