Uh, no. There was LOTS of good material in the 90s. Period. If you think the 90s had a lot of bad comics, you didn't live through the 80s. Or the 70s. Or NOW. The ratio really hasn't changed that much, but the sheer number of titles has changed, allowing there to be more of everything.
And most of the stuff people refer to as '90s' specifically refers to the EXCESSES of Marvel and DC and Image (and occasionally Dark Horse) specifically pandering to specific audiences.