According to those rules, nothing. Except for some occasional AD&D, I spent the whole of the 90's playing games that were released in the '80s, or the '90s release was a new edition, such as the D&D Rules Cyclopedia ('91).
I mostly played 4th ed. Fantasy Hero, which was the first truly unified version of FH, with its version synced with the Champions 4th ed. "Big Blue Book". FH 1st ed. was a late '80s game, but was a very different game than what came later.