Perhaps it's too soon to categorize the '90s, but it was the time I broke in, so I'd call it the decade of cross-genre, which led to the rise of urban fantasy/paranormal romance.I like this answer.
Bruce Sterling coined "slipstream" in 1989. The Sterling-Gibson steampunk novel The Difference Engine came out in 1990. And cyberpunk can possibly be described as cross-genre, since it combines science fiction with noir detective. Sterling has a lot to answer for.
So starting around 1990 or maybe earlier, we have science fiction/fantasy that is mixed with literary fiction, noir, romance and so on.
Science fiction was always a pulp fiction, that borrowed from other kinds of pulp fiction. But I still think we are looking at something new. Now we have writers like Jonathan Letham and Michael Chabon, who are so literary that they are barely in our field, as well as of hordes of steampunk and paranormal romance.
At the same time, we have the New Space Opera, which revives old science fiction tropes or gimmicks, sometimes using them in interesting ways. The expansion from the claustrophobic, near-future world of cyberpunk was a relief, though I wonder what it tells us. The last time space opera was popular was the 30s and 40s, a time of very great stress and threat.
The range in New Space Opera goes from Lois Bujold's Miles Vorkosigan stories to Iain M. Banks' Culture novels. Bujold began publishing in 1986, and most of her Vorkosigan stories came out in the 1990s. The first Culture novel came out in 1987, and Banks has continued producing them up to the present time. One thing true about both Bujold and Banks is, they know they are playing with cliches. There is a certain lack of sincerity in their treatment of space opera. Bujold uses it to talk about 'family' issues: reproduction and disability, love and marriage. Banks produces space opera that makes clear the brutality of war fiction, even if dressed up with ray guns and interstellar fleets.