Upon it's release in Summer 1998 Unreal marked a new era in many fields:
- graphics (one of the very few 3D games of that era that look good even today; no one, I say no one who experienced the SHOCK after exiting Vortex Rikers will ever forget that moment)
- music & sound (one of the rare games that I ever listened to soundtrack from on a CD; the first use of "event-driven" music
- story (hey, it was BEFORE Half-Life! You could end the game without knowing a line from the story, but for an attentive gamer it provided a breathtaking one)
- overall scale of the game - it was huge then and it is now (they just DON'T make games that big nowadays)
- weaponry - with multiple modes for each weapon and combos
- multiplayer - with bots & stuff
So, just to sum it up - if you haven't played Unreal, do it now. It's now one of those "once great, but now outdated games" (eg Wolfenstein, Quake 2, Doom for that matter) that you can play out of nostalgia only now - it's still unsurpased in many areas. It is - pardon the cliche - UNREAL.