BfA. It is so well done cinematically. Great iteration of the story characters, Sylvanas and Anduin looking great!
Shame the expansion didn't live up to it.
I recently watched Legion one. I for one really dig Varian speaking through the whole cinematic. For me, Varian and Anduin Wrynn are the best story related characters in World of Warcraft. Anduin is probably my favourite. So the Legion cinematic got so much depth to it imo, its really good.
Vanilla too of course. The music and introduction of races and classes is what makes it so good. Its a hook-trailer. And, its 20 years old. Just WoW.
My favourite Warcraft cinematic is Grom Hellscream and Thrall vs Mannoroth from Warcraft III. Now thats legendary.
(Best one of all from Blizzard, Starcraft II: Legacy of the Void, a masterpiece)
From best to worst:
BfA(Epic from start to finish)
Vanilla(Just WoW)
Legion(Father and son, relateable)
Shadowlands(admit it, tearing up the sky was epic)
MoP(Best music)
TWW(Manduin)
WotLK(Arthas was a big manbaby, RIP Terenas)
WoD(We are liberators?)
TBC(Best expansion, still not prepared)
Cataclysm(Meh)
Dragonflight(no)