Some great fighters have great amateur careers, like Donald Curry. What great or good boxers have HORRIBLE amateur records? Librado Andrade was 3-13 as an amateur.
I'm sure alot of older fighters that were less "cute" would have had less-than-stellar amateur careers. The way the sport is fought nowadays, amateur boxing is alot more similar to professional boxing than it was back then. It's alot harder for a guy with a REALLY bad amateur career to be even a semi-successful pro nowadays.
I actually think amateur boxing is A LOT LESS like the professional version now than it used to be. The scoring system, 3 minutes rounds, no headgear, that was the old version of amateur boxing and it mirrored the professional sport. Back in the 20s, 30s and 40s, amateur fights, unlicensed "smokers" and small professional club fights were all more or less similar.