The AFL in the southern states and the NRL and NSW and QLD should not fear us. The simple fact is that at a national level football operates for the most part in their off season and football doesn't dominate there either. You have the big horse racing carnivals, the real national sport cricket, a grand slam tennis tournament and of course beach weather to contend with. That's what 'sports' fans are concerned with.
I will admit that AFL lost me years ago when I tried to follows the Swans. I has watched it as a 'sports' fan for years on the tv. While I didn't mind it on television the live event looked like watching a bunch of 6 year olds playing football with vast majority of players within a stones throw of the ball and the rest standing around looking disinterested.
I didn't get the fascination live then and I still don't. NRL is also a better tv sport than AFL and has the advantage live in that a mild NSW or Qld winter is always a better experience that a cold Melbourne winter.
p.s. that is a generalisation of the weather, not always the reality, and supported by most Melbournians I know.