Forget the forum on this topic, full of idiots.
I think overall - he is rated about right, maybe marginally overrated.
Let me explain...
He will go down as a first ballot HOFer, for me he definitely is a HOFer but I think many people have him as one of the greatest middleweights of all time, I've heard it banded around quite a lot in boxing media and I dont agree with that, he simply did not prove.
I think he was vastly overrated pre-Brook fight, but since that fight he has proved himself, he has proved he is elite but he also proved he is not a destroyer of good fighters. He doesnt overwhelm elite fighters, he competes with them, and generally ends up in close, either way fights. His skills and speed are B+ and B respectively, but his stamina, IQ, power, consistency are all up there.
But at the end of the day you are a sum of what you accomplished, he had a lengthy reign, which didnt mean much, mostly C and D level fighters, he did show that he is consistent in that phase of his career. But ultimately he would be judged on his win over Jacob's, which was a very close fight, the two Canelo fights, for me both either way fights, maybe you'd lean his way in the first, and Derv which was also very close.
Here is the thing, I think he had All Time Greatness in the palm of his hand in the second Canelo fight and let it go. I said this in the aftermath and whenever I discuss the fight. I think GGG has the ability to take Canelo into deep waters and drown him, but he chose to box and move (well), he just doesnt seem to have the mentality to go for it from Round 1 and let it all go. I strongly feel, in a war of attrition he would outlast Canelo and stop him late. In that second fight, he had a Canelo who was moving towards him and he himself decided to box, he let the moment slip.
So overall - great fighter, he has proved that, even if you call those Canelo fights same as judges. Just not what he was cracked up to be before he stepped his competition up. If you matched him with all the belt holders over the past 25 years, he would win a lot more than he'd lose, but he would certainly lose some. If you matched him with a prime hopkins, I think hes a level below that.
Another moment he missed was moving up to compete with Ward.
Would've been a much better look to move up and lose against Ward than what ended up happening.