Ok, I'll bite. Its more fun than looking at D-list director's reels.
In all seriousness I don't know why one brand would be consistently better than another. If it was like any other industry, talent moved around, hired-guns designed some stuff, companies sold out to other companies keeping only the name intact, sometimes a lesser brand decided to make a statement piece to play with the popular kids, great stuff was overlooked, mediocre stuff was hyped, some stuff got its well earned praise. Some didn't get any praise at all, even if it deserved it. People looked down on stuff because of the brand name on it, and looked up to stuff for the same reason, regardless of sound quality (I was only 5 at the end of the decade so this is all just a guess). You look inside receivers, they don't look that different from one another. And honestly, they don't sound all that different either, compared to some bigger steps that you can take by abandoning receivers altogether. Of all it, I think the best sounding stuff was the tube gear that managed to still find an audience while everybody else was worried about making up for something else they lacked by bragging about weight and wattage and THD. Sounds over pounds, any day of the week.