I think Johnson heads the list--if you include varients-- jonson, johnsen, etc.

an other post suggested checking census data-- but in US, most of the lists came from US Army-- especially during WWII when a broad spectrum of US population was enlisted. Miller was up there too, (again, with varients. mueller, etc) I think it too was above Smith--

the most common italian name (in NYC) is Russo -- the italian "smith" of NY.

According to US Army/WWII records-- griffin is #100 in the list of family names.