Debatable. Hate to sound like the ugly American, but we think the best pizza is in the USA. If you want to debate who has the best pizza in the USA everyone would have their own opinion. But, we have eaten lots of pizza throughout Italy (including Naples) and although it is generally good we have not been overly impressed.
As to Naples, it is a congested and too dirty city with a high crime rate by Italian standards. There are some things worth seeing in Naples (such as the museum) but, for most visitors, the best thing about Naples is its great location near so many better places.