For me, it's the 70s, even tho it's the decade when the axe fell for the global left, the eclectic fashions, the vibes, the simultaneous sense of cultural defiance, despair, emerging technologies and building dread of an unknowable future that we now know so well, gives it an almost otherworldly quality other decades lack
Also best decade for hair
the 1910s/1900s. At least before WW1, anyway. Aesthetically I prefer it for reasons I can't really explain other than "I like it" but also it's the latest to where the world never really felt like it was inevitably going to be the way it is today. WW1 really laid the foundations for the modern world and everything before that feels like there was so much possibility for a radically different world that could have been