Well, they left behind good and bad. Lots of culture, arts, teaching, plants, food, language, architecture, etc. But the Sicilians were never really a part of Italy until the late 1800s. Sicilians are always considered different than other Italians, especially Northern Italians, and a lot of it has to do with their darker coloring. In order to protect themselves from the oppressive rich "white" Italians, they had to create organized crime. The mafia in Sicily was not originally what it is in the US and Italy today. But now Sicilians are looked at similarly to how gangs are perceived. I actually think it's a pretty close parallel. Most Sicilians don't identify with Italy, and really had no part in most of Italy's historical wrong doings. For example, during WWII, they fought against Mussolini and helped the US. So I'd say they created a culture that became oppressed by other members of society and looked down upon, and some of it had to do with Northern African conquest.
But again, it wasn't a serious question, just pointing out the similarities.