I don't know of a favourite persay, but I can tell you the worst. "Chicago Town" brand frozen pizzas are terrible and you should avoid them whenever possible, not only do they taste crap but they are also made poorly. I had a stuffed crust one and left it in the cuboard for 1 day (something that usually doesn't cause any negative effect to frozen pizzas) and the pizza smelt rancid of overpowering alcohol smell and was sticky as hell, I tried cooking it and it was inedible and horrible.
No frozen pizza should end up like that after 1 day of not being frozen before eating.