Hagler fought and beat many murderous punchers. He ate everything that Hearns threw at him and blasted him out. He also beat and stopped the likes of Mugabi, when they fought Mugabi's record was 25-0 with a 100% KO rate !
I like Golovkin a lot, but has he really earned the spurs to be compared with Hagler? Based off what I see on film, Hagler is quicker, a much better mover, better jabber, is a switch hitter and overall about as tidy and composed as anyone. Golovkin's power is unlikely to faze a man who only ever took one count (which was really a slip) and was never close to being knocked out. I think Golovkin may be the real deal, but he needs to fight a better quality of opponent for us to better judge him.
About right - as yet Golovkin appears to have great potential, and despite him yet having done it, I have little doubt that he beats anyone at 160, his real tests await at 168. The fight I really wanna see is GGG - Froch, I think this would provide (as well as being an outstanding fight - almost a perfect matchup) - a real yardstick as to where GGG belongs in the scheme of things. Froch is not just a top fighter at a higher weight division, he also represents a kinda elite gatekeeper. If you can beat Froch you are up there with the very best. Hagler - well, there ain't a way of knowing, all we can do is compare achievements, and as yet, Golovkin ain't really done so much - I believe he has the potential to be a great MW / SMW but realistically it's way too early to tell.