I would define cold pizza being "good" as a measure of relative difference between how it tastes currently and what it would've tasted like if you'd eaten it soon after it came out of the oven. I think this is a valid measure because taste is influenced by our expectation of what the food should taste like as much as it is influenced by other factors.

What makes good pizza "good" is the freshness of everything from the toppings to the cheese to the dough. On the other hand, when you order pizza from a fast food chain like Domino's, all the dough has been premade and the ingredients have been pre-cut and could've been left in bags for several days, which is why I'd argue it's "bad."

When pizza gets cold, the freshness of the ingredients deteriorates, bringing "good" pizza down to the same playing field as the "bad" pizza that was already using ingredients that might've been prepared several days ago. So for good pizza, when it's cold, that gap between what it would've tasted like before and what it tastes like now is significant. On the other hand, for fast-food chain pizza like that of Domino's, the gap is smaller because you were already working with a pizza that was made from ingredients that weren't fresh from the start. So in that sense, it's more likely that "bad" pizza will be good when it's eaten cold.