Eddhead, there is a lot to choose from in downtown Chicago, so much development in the last 5 years. Of course, after living in NYC you'll find the real estate pricing in Chicago a (cheap) joke, comparatively.
Our Mayor Daley has done a very fine job of polishing up the downtown area and the lakefront, he's a big tree lover and bicyclist. All in all, Chicago is a very "manageable" city to live in, has the amenities of a big city, but is realtively affordable.
What, may I ask, does your g/f mean by "northwest", Chicago northwest or US northwest?