The closest thing we had was the System Shock duology, since both predate Deus Ex. Deus Ex was basically accessible System Shock. Having dialogue trees and NPCs without losing the open-ended nature of System Shock's more dungeon crawl-y approach was the real selling point. Well, that and the trenchcoats and shades. The Matrix was such a big deal.
But even then, each of those elements were already present in different mixes in several late 90s games. Deus Ex by some counts was one of the early culminations of the genre blending "everything game" we were all chasing during the 90s. The other was probably GTA 3. I think both of those are fine and they are certainly important games, but I never enjoyed playing them as much as less zeitgeist-y games that were around at the same time. I did spend a lot of time getting Deus Ex to look as pretty as possible, but I certainly didn't finish it and, like a lot of people, I mostly ran around Liberty Island a bunch.
I played more Thief 2 that year, honestly. I played WAY more Hitman than Deus Ex that year. I certainly thought System Shock 2 was better. Deus Ex is a big, ambitious, important game, for sure, but I never felt it quite stuck the landing when playing it, even at the time.