It depends on the toppings used and how it was prepared.
Frozen pizza reheated will apparently be much more greasy than what I'm used to, either freshly made or self made, the latter containing basically no oil/fat that could be greasy.
Also, you're probably used to tons of cheese and pepperoni, while I often prefer just a little bit of pepperoni, and much more ham, bacon, jalapenos and just enough cheese to not see everything fully.
And yes, pizza from many restaurants are much more greasy than self made ones, but not greasy enough to actually get through carton designed to isolate and contain anything inside.