You need to ask Sicilians which are the best beaches in Sicily. They change every year, not only because of who goes to them and how clean they are, but because nature works fast on this triangular island. There’s a beach near me that was twenty yards of soft sand last summer: this year its ten feet of pebbles.
However, there are some which remain perenially stunning, no matter what annual changes may occur. A website called Wiralist used to offer real-time lists in which Sicilians could vote beaches up and down, depending on how they were shaping up at the time. The site is currently being re-designed, so in the meantime, here are some external links to great lists of Sicily’s perennial beauties:
Some of these are chosen purely on the beauty of the beach itself, whereas others (Touring Club in particular) are chosen on the basis of also having clean water, lavish facilities and a lovely village or town nearby to provide holiday accomodation – in other words, the whole package.