I usually play big&small, standard, normal, everything default. On larger maps, maybe you have more choice of cities, I'm not sure. I would say that on the settings I play the number of ideal cities is limited unless you happen to start amidst a huge swath of grasslands.
I like DaveMcW's rule of thumb: If a city can support at least 10 cottages prior to biology (and, presumably, still grow) then it becomes a commerce city. Add to this one strong gpfarm and some production cities (IW + Military + other production cities) and you have a strong empire.
You still have to play the map though.