Speaking Form a hardcore raiding perspective in the top 30-100:
Classic:
Best: didn't play / only casual
Worst: -
Burning Crusade:
Best: BT fighting illidan was epic lore and gameplay wise
Worst: Sw fuck muru
Wrath of the Lich King:
Best: Ulduar yogg+0 and fire fighter was epic and algalon too ofc
Worst: Nax, this joke I cleared in full t6 fresh dinged on day one
Cataclysm:
Best: BoT
Worst: DS, dog raid
Mists of Pandaria:
Best: ToT
Worst: SoO fuck all bosses in there except sha
Warlords of Draenor:
Best: brf backhand was revolutionary epic at this time
Worst: Hfc fuck archimonde and mannoroth
Legion:
Best: NH
Worst: TOV and the biggest fuck in this list helya, the reason we farmed 11hrs maw of souls a day
Battle for Azeroth:
Best: Dazaralor minus Janna
Worst: EP fuck azshara