As pariston said, each era does the best they can with what they have and how much one enjoys it is largely subjective. Like with me, my first impulse is to say that the 90's was when western animation hit its stride, but that's just what I grew up with. I'm sure there are a lot of boomers and gen-X'ers who will swear to the old Hanna Barbara cartoons, even though, personally, they largely bored me as a kid and, in retrospect, the animation was pretty cheap, and they were largely rip-offs of pre-existing TV shows and celebrities. So, as a millennial who has had a decent amount of exposure to varioius media from multiple eras, here are my thoughts on some those media:
Western Animation - This is interesting as the way people have consumed animation has changed over the 20th century. At first they were done as shorts in movie theaters and I would say that the Looney Tunes and Tom & Jerry shorts still hold up amazingly well, at least in terms of their slapstick (Mickey Mouse shorts, not so much). And then of course Disney pioneered animation into full-length movies and Disney movies from just about any era hold up pretty well. But still, it was kind of a niche market with maybe two or three animation studios really amounting to anything. Then we had the advent of television and Saturday morning cartoons, which Hanna Barbara largely dominated throughout the 60's and 70's. And yeah, as I said already, the stiff animation and humor really don't hold up that well. The 80's was definitely a step in the right direction with better writing and more action-oriented shows, but for me the animation is still pretty spotty and the writing, while better, wasn't exactly A-class. But hey, we did finally get Don Bluth providing some much-needed competition for Disney. Then we got the 90's and, yeah, fine, for me this when western animation hit its stride. This was when animators were allowed to go completely nuts. We had Nickelodeon, Cartoon Network, Disney Channel, Fox Kids, WB, and more all vying for kids' attention and they were all pushing the boundaries of what animation could do and get away with. Animation became more fluid and vibrant, the humor was more outrageous, the pacing more breezy and...yeah, it was just a good time to be a kid. Not to mention we had the Disney goddamn Rennaissance. And it's pretty much been the status quo (more or less) ever since, so...yeah, 90's.
Anime - As much as I love anime, I don't feel quite as well equipped to talk about this since, you know, I'm not Japanese and I don't have particularly extensive knowledge of anime in the 70's and 80's. But, oh well, here goes. In terms of hitting their stride, it seems like the anime industry has been thriving pretty well since at least the 70's. So yeah, in terms of doing their jobs effectively and productively with a saturated market, yeah, you could definitely argue that's when the industry took off. Of course, a lot of the shows from that era still feel pretty dated with their animation and writing. I'm sure even the most enthusiastic of "weebs" will likely give them a miss. But as far as me goes, yeah, I'm gonna give it to the 90's again. Just like in America, the animation became a lot more fluid and the writing a lot punchier (heh). And the industry remains popular and productive to this day.
Movies - Movies hit their stride pretty early on and never looked back. Yeah, a lot of black-and-white and especially silent movies aren't going to hold most peoples' attention nowadays, but they were highly influential and some of them do hold up surprisingly well. I would say the 30's or 40's was when the movies hit their stride.
Video Games - Late 80's, i.e. when Nintendo hit the market. Video games were doing pretty well during the arcade era, but the market crash of '83 showed the industry wasn't as secure as previously thought. But then Nintendo came in with the NES and the industry has been thriving ever since. Personally, I think a lof the 8-bit era games are pretty dated and Nintendo didn't really get any major competition until the Genesis and Playstation, so I guess maybe I could say 90's again, but...eh, I think late 80's still earns it.
Rock/Pop Music - The 60's, no question. The 50's set the stage, but the 60's was when all the mad geniuses came out and created some of the most influential and revolutionary music that still holds up to this day.