If he'd looked like that against Barrera I might agree - but a boxer's greatness must be measured against his opposition.
Mayweather Jr and Hopkins are the slickest. No one ever lands anything flush on them. Toney used to be incredibly slick.
slickest ever for me was pernell. the prince fought bums that made him look slick. when he was not fighting bums he did not look all that slick to me. just funny style ass fighter with decent speed and some power and was a lefty.