I don't think there is a ground in Sydney that was more difficult to get to than Waverley (VFL) Park - stuck way out in the remote outer suburbs and with virtually no public transport at all. Getting there and back was an all day expedition, yet it still drew huge crowds.Sydney is an extremely difficult city to get around. Melbourne is not. The only city where you can make fair comparisons is in Brisbane where both the AFL and the NRL only have one team in the city.
But even if we ignore all the other evidence of Australian Football's crowd pulling culture (Subiaco, SANFL, Vic country footy) that extend well beyond Melbourne, and just use your Brisbane comparison, Lions crowds compared to Broncos, it still stands up well, with very healthy Lions attendances, given that we're talking about a rugby league heartland area.
And relating this back to West Sydney, well as I said, I'm not expecting any sort of overnight success - it'll take a generation to build that culture. As I said a few posts back - "once started up there, it might take 20 years to really grow strong roots and be self sustaining, but given sufficient financial support for a number of years, and also investment in grassroots participation in our game, it should eventually have a firm place in the Western suburbs sporting landscape. Just don't expect it to happen overnight. As the old saying goes - "Rome wasn't built in a day".