In what ways were the city-states and civilizations of Africa diverse?

Answer 1

I assume that you mean a fairly long time ago, especially before the eras of colonization and modernity.

Language.
There were five major language families in Africa: Niger-Congo, Afro-Asiatic (or Afrasian), KhoiSan, Nilo-Saharan (or Nilo-Hamitic), and Cushitic (Kushitic). City-states were probably not a part of KhoiSan peoples, but large states and urban concentrations were common to the other four for most of history.

Economies.
Economic activities varied more with environment than with culture. Trade towns grew up where people had surplus food, valuable preservable commodities, and good transportation. The Niger River region is an especially good example of this sort of trade-based wealth. Subsistence economies - even hunting and gathering - existed where those trade-fostering conditions did not apply.

Art.
Everyone had their own art. The Dogon in West Africa have amazing funereal masks associated with death and used in dance ceremonies. Zulus and other southern African women strung beads for self-decoration. In the cattle-raising areas just south of the Sahara, many ritually scar themselves with meaningful marks - not writing, but indications of their maturity, destiny, etc. And as gruesome as it might sound, it's also beautiful to look at.

Religion.
After about 1000 AD, Islam had spread in Africa beyond modern Egypt. It was the religion of rulers in West Africa and of merchants in East AFrican (Swahili) city-states, and increasingly in Central and Southeast Africa, spreading mainly through trade.

Answer 2

They don't speak the same languages. They don't have the same religion, and they have different customs.