There's no such thing as a bad pizza.
That being said...you haven't had a really good pizza unless you have had one from a small pizzeria in NYC.
Spent 2 weeks in NYC trying all kinds of pizza since it's my favorite. To be honest wasn't really impressed. The was one place that was 2 doors down from a Sbarro oddly and hole-in-the-wall - pretty good. But I've tasted mom and pop places out here in LA that were better to my taste. Chicago deep dish should be called Lasagna, it's not pizza.