I was discussing procedural city generation with a graphics person awhile back. One of the things we realized is that procedurally generated cities almost always feel "wrong" because real life cities generally have a mishmash of dozens of general architectural "styles" based on various quirks of history.

One example: in Cincinnati Ohio, working class houses in certain neighborhoods have stained glass windows. It's usually only one or two small ones, but they're there in certain neighborhoods because of a stained glass artisan "scene" that arrived on a wave of German immigrants. Another quirk about Cincinnati: there are lots of houses that are quite narrow for their plan area, because taxes were based on the width of the building on the street. There are quirks like these that cause a city to be a geographically differentiated patchwork of different styles.