I don't recall a lot of by-the-slice pizza in the city, but the best pizza by far in the avenues was Pirro's - fist 21st & Taraval and later on 33rd & Taraval.
I hand-spun pizzas there for 6 years from '68 to 74 - not counting my time overseas in Uncle Sam's Yacht Club.
Our biggest competition was Pasquales on Irving and Toto's in Daly City.
Sadly, from what I hear, Pirros isn't even a shadow of its former self, and hasn't been for some time. Pasquales opened up a second delivery/take-out place at the old Jumbo's on Sloat and I'm told it's just an adequate pizza.
As for that QFI Pizza?!? I'm pretty sure it was sausage - but with so much filler, the pork was barely an oink.