I don't know how they choose all the city states, and I may be ignorant, but some of them were totally unknown to me before playing Civ V: Almaty, Ragusa (from top of my head, but i know there was some others...)
about the "too much italian cities", IIRC, there are only 3, Genoa, Florence and Venice. To me, they were obvious choices like Vienna, Bruxelles, Prague, Copenhague, Montreal, Rio de Janeiro, Kuala Lumpur, Budapest (is there Bucarest too?), Dublin, Le Cap, Seoul...I think i saw Amsterdam too
I disagree with the choice of Stockholm, Helsinki, (I think there is Oslo too), that's too many scandinavian cities...why not Reykjavik?
There is not enough african city states (Carthage/Tunis, Nairobi, Dakar) or latin american (Valparaiso, La Havana, Panama...)
I acknowledge it's harder to find some great non-chinese, non-japanese, non-indian, non-arab, non-siamese, non-persian cities, non-mongolian, asian cities but two comes from the top of my head: Lhassa and Jerusalem...(besides Kuala-Lumpur)
I know Jerusalem is too touchy to get in, and I think there would be much debate about Lhassa being chinese (bet someone will say that Lhassa is in China!!) Finally, I don't think Kaboul is eligible to be a city state...
However, since, Oulan-Bator never was a city state (because mongolia was supposed to be a DLC), i conclude that not having Madrid, Sevilla or Barcelona, means Spain will be a coming DLC!!!