Like London had a hard act to follow after Beijing.
The true is that every Olympic is different. China laid its own mark when they hosted, London laid its own mark now and Rio will do the same in 2016. Rio will have its ups and downs but in the end, I'm sure it's gonna be fun and enjoyable party.
I don't think the brazilian organizers have to worry about London too much, they have to make their own Olympics now and hopefully people in the world will enjoy it, if not, I'm sure brazilians will love the experience either way. This is gonna be a south american Olympics, like it or not.