First of all i know that The Simpsons were around in the 80's and their still around today but to me the decade for The Simpsons was the 90's. During the 90's The Simpsons was at it's most popular especialy during the early 90's when Simpson's mania was huge. So whenever someone mentions The Simpsons to me the first thing i think of is the 90's

To me, the quality began going slightly downhill in '98, although it still made some classic episodes until 2001 or so. But yeah, I always saw as permanently being a part of the 1990/'91-1998 "zeitgeist" (starting in the first couple seasons when Bart was more the star of the show) that has simply adapted itself for the changing times. It almost seems like Springfield is rooted in the early-mid '90s with outside influences of the times afterwards.

The first episode was on the 19th December 1989. The Simpsons has nothing to do with the 80s at all.

As for the 00s, yes it's still around but it's not making as big an impact as it did in the 90s. They even discontinued the Simpsons action figure line in the 00s. Maybe the new movie will change that.

The Simpsons started off in 86/87 (Can't remember which year) as shorts on The Tracy Ullman Show so they were around in the 80's but if your talking about full length episodes then your right The Simpsons had nothing to do with the 80's

By no means would I call it an '80s show, but if you watch the first season or two(when the animation was crude, and Homer had his Walter Mathau-esque voice, lol) I do think it had a tinge of that campy Home Alone-era feel about it, even if just marginally.

I think it depends how long something goes on as for what it'll ultimately be defined as. I mean, if it were a relative flop and only lasted two seasons, we'd probably be calling it a "late '80s" show (not quite literally, but the way, say Fresh Prince or Saved By the Bell seemed to always have this 1989 or 1990ish vibe over them). However, since it had lasting success, the image changed along with it.