Easiest conclusion is GGG had the harder fights.
Golovkin faced Jacobs and Brook,
The Can faced Smith and JCC JR.
Brook had a chin and was undefeated, also beat Porter, has power.
Jacobs was a stronger and more active fighter who dropped Peter Quillin. Both Brook and Jacobs coming off wins.
JCC last fought at 160 in 2012, got knocked out at lightheavyweight. Last fought a bum in Mexico.
Liam Smith - never fought outside UK (Brook didn't either). was a young champion with a belt off a no name. No strong power. Fought at 154.
GGG fought the tougher guys, Canelo handled his fights well but it's no comparison.