I can understand complaints about Sydney - architecturally, it has some amazing highlights (Sydney Harbour Bridge, Opera House), and there are some nice beaches, but that's about where it ends. Melbourne is much better as a tourist destination - no matter what your interests (sport, culture, food, shopping), Melbourne has it, and all within easy walking / tram distance.
I wouldn't rush back to Venice. I didn't find it romantic - just throbbing with tourists.