i think that Arnold's advantage was that he spent many years training naturally and started at a young age. That, plus he continued to train whilst off gear and had definite cycles.
So he had a solid foundation, trained his brain to understand what hard training actually was, and that gains werent guaranteed or easily got. So when he went "on" his body responded well, his intensity was high, and expectations realistic.
All that together probably makes him, and others of his era, better bodybuilders- which is why the drug sponges of today still look upon him in awe. Granted he had great genetics also.
I wonder how many out there these days have good genes, started at 14 or 15, trained naturally for 3-4 years, then do actual cycles?...i'd guess very few.