The 90s weren't great. We had wars in Yugoslavia, Chechnya, and more.

But, in general, I do have a sense it was a uniquely optimistic decade for many people in the former First World, mainly because the Cold War ended and there was a sense that we had "won". Western Europe in particular demilitarized a lot as a result, the EU was formalized, the Good Friday Agreement was signed, Oslo Accords happened, end of apartheid etc.

For Americans I think 9/11 derailed things again.

Outside of the former First World, I'm not sure they'd see the 90s the same way.