What serious boxing fan doesn't rate quality over quantity when judging a fighters record? If the 50-0 fighter has fought a load of bums and the 30-3 fighter is proven world-class everyone will consider the latter superior.

Considering you only mentioned Canelo and Chavez Jr in your original post I guess this is about them.

If you chop the bottom half of Canelo's record off, for a 22-year-old, at 20-0, with a bunch of former world champions and challengers on his record it's still very impressive. And Chavez Jr, as weak as his overall record is, nearly knocked out a P4P star and the lineal middleweight champ.

So even if they have bloated records, they both proved themselves at world level.