The only frozen pizza I like is DiGiorno. Though, at my local walmart they have the big XL pizza that taste good also. It can become hard to choose between the two though.
For the price I also tend to favor Red Baron pizza. I am in the same position as gracie, however, for whatever reason my significant other favors Jacks Pizzas, which I guess are okay, but they aren't quite as good to me. They're also smaller, which sucks. For a slightly higher priced pizza I really like California Pizza Kitchens frozen pizzas. I don't care for the self-rising pizza's Freschetta has, it seems like way too much bread...
DiGiorno is pretty good and has a fair variety, and I actually really enjoy Target's store brand ones...but overall favorite I'd probably have to say California Pizza Kitchen. They're not badly priced and are very good .