You've been Doing it Wrong!
Don't know if this one has already been around on GB, but...
All these years...and you've been doing it wrong! Well, I have anyway.
The proper method to reheat cold pizza is not in the microwave. The proper way is to use a lightly greased pan. Place your pizza in said pan after it's nice and hot on high heat. Cover the pan for a couple minutes. Voila' no more soggy reheated pizza! Tastes just like new, nice crunchy crust and melty cheeze with hot moist toppings! Yum!