A new "points of interest" feature was recently added to Google Maps. Areas with a certain unknown density of points of interest are drawn in an orange-y shade while other built-up areas are shown in grey and parks are drawn in green. I was surprised at how closely the "interesting" areas map onto parts of cities I'm familiar with that actually do have a lot of stuff worth exploring (some of the areas of interest are just malls, but those are usually easy to distinguish from the storefront areas based on the street pattern).
You can see this for yourself at
http://maps.google.com/
This isn't exactly a rigorous or scientific way to compare cities but I thought a few different maps were interesting. Here are some of the cities I looked at, mostly the ones I'm familiar enough with to comment on. They're all scaled differently.
Toronto. You can see how commercial areas stretch out along major streets like Danforth Avenue. There aren't a lot of "clusters" of commercial areas outside of downtown, and the west side of downtown is more developed than the east. Some parts of the central business district, as in many North American cities, despite being heavily built up don't actually have a lot of publicly-accessible points of interest.
Montreal. More of an eastern (really northeastern) bias to where the points of interest lie. You can see some gaps between the old town and newer downtown area.
Vancouver. A lot of the downtown peninsula has points of interest, although parts of the West End are more residential. Off of the peninsula the city follows a Toronto-style pattern along streets like West Broadway (East Broadway is quieter) and Commercial Drive.
Quebec City.
Halifax. More of "blobs" of commercial activity rather than long streets (it looks like it has a vaguely gridlike street network but it doesn't, and it has few long ateries in the old core; maybe that's part of the reason for this pattern). There are some little commercial nodes in areas like Gottingen and Kaye Street (Hydrostone) and there is even one way out on Dutch Village Road. Dartmouth has more than I would have thought. Agricola didn't make the cut; maybe in a few years.
Charlottetown. The older part of town is pretty active.
London, for comparison's sake. I'm not sure if the reported "points of interest" are comparable across national borders but London unsurprisingly has comparatively extensive areas with a lot of them.