Man, looking at my post last night... that was some damn disjointed rambly stuff. Not my best work...

Trends... unified die mechanics weren't important but consistent use of dice methods & mechanics was... clear game mechanic goals stated in the books were a plus... player facing stunts & abilities were more fun than those requiring gm work... higher expectations of systems functioning without gm changes/rules work for paid systems & it scaled with $$ spent... huge lists of **** to wade through for a few good choices was a turn off... huge lists to wade through where everything was useful was a plus... a speed of play vs gm workload vs player workload thing...
My memory is a bit hazy on it, been a good while since then. Memorably tho, the D&Ds & knockoffs got lower ratings as the edition numbers went up, with an inverse between AD&D 2e S&P to 3e but a return to pattern with 3.5e.