IMO it's Bernard Hopkins, but I do think Gennadiy Golovkin is overall the better fighter between the two.
Hopkins beat John David Jackson Glen Johnson Felix Trinidad Carl Daniels William Joppy Oscar De La Hoya (washed up) Antonio Tarver Winky Wright (washed up, catchweight) Kelly Pavlik Roy Jones Jr (washed up) Jean Pascal Tavoris Cloud Beibut Shumenov ggg beat Kassime Ouma (washed up) Matthew Macklin Daniel Geale Martin Murray Willie Monroe Jr David Lemieux Kell Brook Daniel Jacobs Sergiy Derevyanchenko Ryota Murata Hopkins has the better resume
Better to compare their Middleweight reigns only as they have a similar number of defenses. Hopkins has done solid work at Light Heavyweight which completely establishes his resume many cuts above.