From your point, won/loss records at that time meant less because fighters fought way more often to make ends meet. In other words, a guy who was 25-25 might have only been a professional for two years, and because of the number of fights, might still be a novice at the professional game. So, it's difficult to accurately gauge how good some of the guys with so-so records actually were.
As to Floyd, I'm sorry but there is real reason for criticism at the choice of Maidana. Floyd is a former Olympian, undefeated professional, with a record of 46-0. We can poke holes in his record, and talk about the guys he missed on his way up, sure, but no one can deny he's at least one of the best in the last 20 years.
Floyd's facing
Marcos Maidana. The odds are 15-1 in favor of Floyd.
Speaking of built up records, in a day and age where fighters fight 2-3 times per year, Maidana, who is 35-3, fought guys with losing records until his
14th professional fight and, even then, in his fourteenth fight fought a guy he had previously knocked out. Moreover, he did that
in this day and age, not when fighters fought 50 times per year. He didn't even fight anyone recognizable until his 27th fight, when he
lost to Kotelnik--which means that he has only been operating at the world level for approximately ten fights. His only notable wins have come against Broner and Ortiz. Ortiz never won a big fight and Broner, well, Broner is Broner. Devon Alexander took Maidana to school. So, yes, Maidana is better than the 3-5 guy on Greb's record, but he ain't nothing to write home about either.
Floyd's the biggest name in boxing. He's the self-proclaimed
TBE - The Best Ever. Frankly, the question is not why people would be hard on Floyd when he fights twice a year for choosing Maidana as an opponent: the question is why wouldn't they? If he fought five times a year, Maidana is maybe just ok as an opponent. If he fought 10 times, which is far less than Greb did, Maidana makes more sense. Conversely, if he fought 30 times a year, Maidana as an opponent might be damn impressive. If he fights twice, however, fighting a guy who has faced guys with losing records in approximately half his fights, not so much.
Speaking of Ruslan, he has 25 total fights. In this day and age when fighters fight two or three times a year, 10 of 25 of his opponents were against guys with losing records. Giving him the benefit of the doubt, there are probably six recognizable names on his resume. He lost to two of six.
So, how can we be certain Maidana and Ruslan are quality when almost half of their opponents have losing records and they have lost on multiples times when they step up? How much credit do we give Floyd and Manny for facing them?
Greb fought 30 times in 1919. Keeping in mind there are 52 weeks in a year, he fought Battling Levinsky, who is in the Hall of Fame,
three times. He fought Billy Miske, a tremendous fighter. He fought Mike McTigue, another tremendous fighter. He fought Willie Meehan, antother great fighter.
In the same year. Maidana isn't making the Hall Of Fame unless he shocks people come Mary 3rd. So, let's give him the benefit of the doubt and same somehow he compares on a p4p sense to McTigue or Miske Or Meehan. Greb fought three guys at his level in the same year that he faced a Hall of Famer in Battling Levinksy three times and fought a total of 30 times. By the way, 1919 wasn't Greb's best year.