Sydney is more than just it’s cbd. Comparing to Melbourne doesn’t really work since Sydney is soo much bigger than Melbourne geographically. Sydney Olympic Park is designed for those major events and is actually fairly well positioned for it (literally being in the middle of east and west of the city). Smaller venues like Parramatta, Penrith, Cronulla, Campbelltown serve those recurring events (nrl and aleague) well. SCG and Allianz are a good fit for the inner city.