Kind of like Yanks/Mets I suppose.
It's interesting... as a generality (not a rule) the Sox fans really, REALLY hate the Cubs fans. The Cubs fans are so into themselves, their mistique, their bad luck, thier history, their amazing ball park, their players of old (Ernie Banks, Ron Santo, Harry Carry, Ryne Sandberg) that they generally pay no mind to the Sox fans. There is also a slight socioeconomic battle going on as well. The South Side is generally considered the working class hard fighting type, while the North Side has a bit of wealth associated to it's identity. Although there are millionare Sox fans, and dirt poor Cubs fans, this undertone does exist and helps create the many layers of rivalry that exist between Cubs and Sox fans.