I'd love to say Shadowrun, But that came out in 89.
Sooo. Expanding on prior.
Torg: 1990: Great system and setting that offered alot of versatility.
Rifts: 1990: Feels more 80s. Another great system that offers alot of versatility.
Nightlife: 1990: Rather nice little alternative to WoD.
Dream Park: 1992: Another nice little Talsorian RPG that has fallen into obscurity. Based on the novels. And another nicely versatile system.
Macross II: 1993: An odd standalone book using the Palladium Macross system. Based on the equally odd standalone OVA.
Wraith-The Oblivion: 1994: I really like the original version of Wraith. Really unusual premise rarely seen.
Defensores de Tóquio: 1994: Brazilian RPG that is fairly well done and also fairly versatile despite its focus on Japanese Superhero/Sentai adventures. Features ALOT in Dragão Brasil.
Dragon Storm: 1996: About the only real CCG-RPG ever. Excellent system and liked it so much I designed some cards for it and footed the bill for the art and had a little business agreement with BDP and my own little company back then.
Cthulhu Live: 1997: Direct conversion of the CoC RPG into LARP rules rather than an actual RPG in the normal sense. What for me really made it shine was the Shades of Grey expansion which converted it into a Pulp Hero LARP!
Aberrant: 1999: WoD system used for a gritty superhero setting and done right. Miracles do occur! This is one of my favorite superhero RPGs alongside TSR's MSH.
Furry Pirates: 1999: I was a playtester for this way back and despite the Disney Robin Hood animals theme, it is a surprisingly well done historical accurate RPG covering alot of details and personalities spanning the age of sail. I also like it more than its predecessor as the magic system is both optional and far toned down.
So of those probably Aberrant tops my list followed by Dragon Storm, Torg, and Cthulhu Live+Shades of Grey
I left out Buck Rogers as realized the version from the 90s was not the same. Its not a bad little system. Just not my thing.