I would say he is overlooked. Not a top 10 middleweight by any means but he is a deserving HOFer. Had the ability and the longevity to have been a top middleweight in any era. He was not a flawless fighter though and could be beaten, even by lesser opponents. You have to take into account that he fought in one of the strongest middleweight eras too. There are many fighters who are called great nowadays, that wouldn't have lasted in those days. Fighting as frequently as he did against opponents perfectly capable of upsetting anyone on any given night and sometimes with little preparation, you'd expect him to have had his losses.
As some boxing writer said of Billy Graham,"he was as good as you can be ,without being GREAT ". This too applies to Joey Giardello. Sly, clever and methodical was Joey Giardello...
He was as tough as they come. Granite chin and all kinds of guts. Couple that with clever, durable and a fairly good punch. In any era and on any given night, he could beat the best there ever was. He by his own admission wasn't always in the best of shape, but when he was, look out.
That's what stands out for me, his toughness. His boxing ability being wat it was, that was what people always want to focus on, but he was a rugged *******.