Mark, Aussie Rules is really GAELIC FOOTBALL...its just a different name, and some slight rule changes and a different ball. It's a disgrace to Australia and gives us a bad name.
Domestically though, All 4 Football codes are played in every state, whether big or small.
Cricket is NOT necessarily Australia's national game..its more of a recreational game. I know many Australians that can't name the players on the Aussie team. But i guess everyone likes to enjoy a bit of backyard cricket here and there.
Football(soccer) has the biggest international appeal with the national team competing on the world stage but the domestic teams are the least supported of the 4 Footy codes...
Rugby Union is has a good International game and the Wallabies are the most supported national team in the country, the domestic competition has good support too but not over all of Australia...
Rugby League has a smaller International game but pretty good domestically and sells more merchandise than the AFL or Super 14. But really is only popular in NSW and QLD.
Aussie Rules has NO INTERNATIONAL GAME! They boast about their popularity in Australia but the reality is that besides the minority of the world living in our remote continent, Aussie Rules doesn't even show up on highlights overseas.
Australia's game though, i hate to say it...would be Rugby Union.