Like most, I qualify this by noting that frozen pizza isn't pizza (or at least is a variant style that's FAR different from any other... after all, NYC and Chicago are almost incomparably different as well).

That said, I've found most of the fancier/oven-rising crust ones to be absolutely not to my taste - bordering on inedible - and the cheaper, more basic "crisp crust" ones relatively palatable for whatever they are. I'm also a relative purist when it comes to toppings, being from NYC originally and of the pizza-by-the-slice-is-best school

Even among the frozen pizzas I like, there's a big difference between the "heavier crust" ones and the "puff crust ones" and I'll rate them separately:

Heavier crust:
- Tombstone is best with pepperoni, as their "extra cheese" is kinda bland but their pepperoni are tastier than the ones on Tony's.
- Tony's is the best plain cheese, with tastier cheese and a lighter and more predictable cooking crust than tombstone.

Red Baron is a barely acceptable alternative to either of the above.

Lighter crust:
- Gino's Crisp and Tasty /or/
- Totino's Party Pizza are both acceptable, and have the advantage that one makes a decent meal for one on its own (whereas any of the heavier crust ones are easily enough for two) They also often fit into the toaster oven.

Celeste brand is allegedly microwaveable, and nasty when microwaved. It's a barely acceptable alternative to the above two when cooked in the oven, however.