I largely agree but you're wrong about the weights. Hagler weighed pretty much exactly the same as GGG. Both about 170-172 in ring. I'm less sure about Canelo but I'd guess he's a half stone more...about 178_180.
Canelo is better than anyone Hagler beat at middle except Hearns and Griffith along wit Napoles would have given Hagler problems both of them were more impressive in their fights with Monzon than Ray was v Hagler, I don`t feel Ray won at all.
Your joking right Mugabi would do just fine against both GGG or Canelo. I mean come on you think Lara and Trout would be top guys in that era no way jose!
Im sorry my view is different but the guys back then were just generally better and alot more active fighters,, Trust me buddy there was no gimmie fights back then you had to pack your lunch even against the bums in those days
One of the handful of American fighters of the last 50 years who was capable of hanging at Brit Level or if not quite that high just below it. So the answer is very high.
A quality hardworking boxer , who has glory , timeless fights and is up there with the best of the best honestly .
I was around then. I know what the standard was. I'm certain GGG and Canelo would cope in that era, or any era.