For most of their shared history, Athens and Sparta were on neutral or friendly terms and their interests aligned or at least did not conflict. So saying the Spartans and Athenians disliked each other is a generalisation akin to saying that the English and the French have had amicable relations throughout their shared history. read more
Hmmm if you place your question in the present, the answer is that they do not really hate each other. If you refer to the ancient city states, the answer is very simple too. They actually had no real hate between them but just 2 major problems. firstly different political views. read more
The two city-states that best represent each form of government were Sparta (oligarchy) and Athens (democracy). The democratic government in Athens, though decently equal, fair and fairly advanced for its time, did not meet the needs of the Greeks. During a time of many military battles Athens decided to worry more about comfort and culture. read more