I think São Paulo is a city that takes time to discover. The only people who like it are those who've lived there long enough to be very familiar with it...since it obviously lacks the "postcard" sights of Rio.

I lived in both cities and I loved Rio, despite its problems. I found SP to be quite boring, grey and overcrowded (save for select places like Liberdade, Ibirapuera, the former Portuguese Language Museum, Serra da Cantareira, etc), yet I always thought that if I had lived there much longer, I could have grown to really like it. There's a feeling that something pulses under the surface and you can only experience it via serendipity, word of mouth and curiosity, if that makes sense.