I don't have one single answer unless you define your question more by asking what is your favorite chain, national, or local pizza.
When I think pizza, right away I think of a small pizza shop owned by some guy named Tony or Sal who spins his own dough. But, of the national brands, I like Pizza the Hut's Pan Supreme, its even good the next day. Papa John's is a good pie, but not a very good morning after pizza, it must be eaten hot the first time around. And locally, it's a tie, V&S has the best Sicilian and the original Bella has the best thin crust.