[clock_tower]

Buildings which are just residential (and, for that matter, ones which are just commercial) still tend to produce dead zones, with little to no street life; and it's street life (and walkability) that makes a city, at least if you ask me.

I'd say that the best kind of city -- or district/neighborhood, more accurately, since cities tend to be a patchwork -- is an area of multi-storey buildings with businesses on the ground floor and apartments above them. My understanding is that this is the usual pattern in the Old World; in the US, the North End and Allston-Brighton in Boston, Seattle's Chinatown, and of course Vancouver are among the examples. This isn't a common pattern in the US; I know that parts of NYC fit it (although I don't know that city particularly well), but I've heard that even Manhattan Island is all office buildings, and becomes a wasteland after dark.

I certainly agree, though, that 4-9 storeys is a pretty good height. Smaller than that and you don't get enough density to support interesting streetscapes; larger, and you get wind tunnels and the need for more parking. Of course, sometimes geography (San Francisco, Tehran, most of Japan) or politics (Singapore) force a denser population, and require a more built-up area...

[ild]

USSR has always had ground floor shopping on the street facing residential buildings, also major bus stops have convenience stores attached.

[clock_tower]

It sounds like I should visit Russia, then! Whatever else can be said about them, it sounds like the Soviets really knew how to build a city.