This game had the storyline, that the others didn't!
In Quake II I liked the story. And another thing that I noticed while playing was that sometimes the enemies fighted each other, when an enemy accidentally hit another type of enemy and then they started to fight each other.
Then came Quake III and Quake IV which were like unreal tournament, but at least unreal tournament had story.
I think Quake II was the last real Quake.
Graphics were great for an old game.