Try this one: name major market share roleplaying games currently in existence that were not first published in some form in the 1980s. I can think of Rifts (1990) and Vampire (1991). Mutants & Masterminds might qualify.
That kind of proves that the 80s WEREN'T a golden age for RPGs entirely. For a long time, the two biggest competitors to D&D's crown were RIFTS and WW. Both of which are 90s era RPGs.
All of the 80s era RPGs never were popular enough to garnish ANY market share from D&D whereas those two did.
(Hell, throw in Shadowrun which was big in the 90s and came out in 89)