karenlaughlinis, what are your interests? Why are you going to Italy? People have different reasons.
Most people who follow Rick Steves and his Italy books and TV shows probably knows he's been a vocal promoter of the Cinque Terre for a while, which some believe has made the area too popular. I have been there a few times and love it and have yet to make it to the Amalfi Coast (which I understand is beautiful - but my Italy trips have mostly been focused in the north).
I'd say the big appeal of the Cinque Terre is hiking. It's a beautiful area on the coast in the Italian Riviera with picturesque towns that look almost like they were built into the side of the hill. Hiking between them is a favorite activity of many tourists. You can hike through olive groves and sometimes even past people's back yards, often with breathtaking views down on the ocean.
If you are not hikers, personally I'd skip the area - it's going to be crowded in September, and the downs will be mobbed with tourists mid-day (quieter at night but not desolate). If you still want to visit the Italian Riviera, you can always visit towns north of the Cinque Terre like Santa Margherita Ligure, Rapallo, and Camogli - all lovely towns but with far fewer tourists in September than in the Cinque Terre.
If you're more into food than scenery, maybe Emilia-Romagna (Moderna, Parma, Bologna) is going to be more your speed. The food is amazing. I preferred Parma to Bologna personally (haven't been to Moderna). But most people don't visit these places for the hiking opportunities.