Well, I've been living in Italy for 5 years but, honestly, I haven't visited much of it.
To answer some of your questions, what makes me want to visit a place are the pictures I see on the web. Sometimes I also see some of my friends' or colleagues' pictures from their vacations and I immediately get a feeling of "I have to go there someday!".
Among the few places I have been, the most beautiful one was the city of Genoa. It may not be among the most famous cities of Italy but to me Genoa represents perfection: seaside + mountains. I've only been there once though.