I don't know much about Xavier, but Cincy always struck me as recruiting a lot of "marginal" student-athletes. Couple that with their style of play, and they can ugly things up pretty quick. These two teams share a city, recruiting territory, etc., so it makes sense they don't like each other.
Syracuse and Georgetown is pretty much dead at this point as far as heated rivalries go (I still hate Georgetown though). JTIII was too decent of a person, and they don't recruit the Michael Graham, Victor Page, Allen Iverson types anymore. Our team is almost always more finesse than scrap.
Duke and UNC are obviously pretty heated, but they tend to both recruit petulant, whiny brat types. I think their fans despise each other far more than the players.