For chain pizza, I like Mamma's
Then there is Bitondo's, just south of the little Italy strip (and right near California Sandwiches, which makes probably the best veal parm in the city) which is amazing pizza and their decor and signage looks like something that oughta be in Brooklyn instead of Toronto
And, in the east end, near where I grew up is a really good place called Colombo's (on Danforth just east of Coxwell) where the same family has been makin' the pies since the 60's
Man, am I hungry for pizza now....