The trick against Australia is attack their batting with good bowling. Then you will have real chance beating them. But if you allow their batting to flourish with your weak bowling, then they have decent bowling line up to attack you & win the game. Teams like India, Sri Lanka will struggle against Aussies until they find a decent bowling attack to put pressure on their batsmen (that mostly happens in Sub-continent conditions where India & Sri Lanka & even Pakistan can dominate them with their bowling). But on their day Aussie batsmen have the capability to pile up huge runs at real brisk pace and their bowling can take care of the rest. Which means Australia are the "first" favorites to win the world cup especially when they are playing at their home (can happen like how India won the world cup at their home)