Haven't bought pizza in Portland in over a decade, but DeNicolas and Old Town were good back then. For chains Pizza Hut or one of the take-home Papas (Aldo, Murphy, John). Abby's in Bend is good, as is Ponderosa pizza in La Pine.
There was a place at 39th and Powell back in the day (late 70s) which started with a "P" I think, and they cut their pizzas into little parallelograms instead of slices. Anyone know what I'm talking about? Damn I miss that pizza. barfo
I bet it's been mentioned, but Dove Vivi over on 28th and Glisan is amazing stuff. Cornmeal crust is the key. http://www.dovevivipizza.com/
julianos in the couve is the best pizza i've ever had. the flying pie is a close second. i also support the blind onion and their dough made daily by sunrise bagels.