I've had Italian Pizza, NY Pizza, California Pizza, Chicago Pizza, and pizza from god knows how many other places.
I'd say my favorite chain pizza comes from Zpizza which is an orange county establishment. But seriously. New York Style pizza with Tomatoes and Basil is delicious. I like it when the slices are so huge that you have to fold them so as to be able to eat it.
Overall though, Thick crust with Jalapenos and Pineapples will make me happy wherever it's from.
Italian pizza isn't really pizza as we think of it. It's more like a pita that you cut with a knife and a fork. Like a margarita pizza that isn't pre cut and is smallish. I make them pretty often. You can make the crust super easy. 1 part shortening to 2 parts flower with a bit of salt.
On a side note... I forgot the name of the place, but there is this place in Pasadena that makes 3ft by 3ft pizzas. AMAZING!
Oh, and California doesn't have it's own "style" of pizza. we just use the same type of crust as NY but the pizzas are normal sized and we have way crazier toppings.
My favorite Pizza from Zpizza is the Mexican, "salsa, mozzarella, spicy lime chicken, green onions, red onions, fresh avocado, sour cream, cilantro"
but the thai pizza is a close second, "peanut sauce, mozzarella, spicy chicken, red onions, cilantro, carrots, bean sprouts, serrano chilies"