If I had to pick a well known 'chain' pizza, It would be Domino's Philly Cheese-steak pizza (minus the mushrooms, of course).. although I've grown quite fond of their Fiery Hawaiian pizza as well!
Otherwise, there's a chain around here called "Fox's Pizza Den" that just whips the pants off of everyone else. They have a Bacon Cheeseburger Pizza that is simply delish! They also have incredible strombolis!