I think the Golden Age of The Simpsons is seasons 2 through 9. So many great moments during those years. I think of seasons 10 through 13 as the Dark Ages. Those years had some funny moments, but overall weren't that great. I think The Simpsons has rebounded these past few seasons, but it's still not as excellent as it was during those golden years.

The Mid and Late 90's. Between 1992-1999.

From the first season to the 9th season in my opinion.

I think the first 10 or 11 seasons were the golden years. Then it started to go down hill for a while till season 15 when it rebounded. There were some good episodes in between but I think it didn't really rebound till season 15. And now the Simpsons are good again. They aren't as good as they once were but I think their good again.