Barefoot_Monkey: Not exactly. It used a mouse pointer for interacting with the UI and objects on the screen. You
could use the mouse to aim in any directyion, but it wasn't quite "mouse look" as most understand the term. It did, however, use the SZXC keys - exactly like WASD but one row down (W, A and D were used for running and turning) so it's a good example of almost-WASD.
If you think the System Shock was amazing for it's time, consider that its predecessor, Ultima Underworld, was released
before Wolfenstein 3D. For me, that's almost as mind-blowing as Euler's Identity.
I vaguely remember a story about how one of those engines 'inspired' another engine, either Id borrowing the technology for Wolfenstein or something like that.
It was a long loooong time ago I read that somewhere.
But anyhoo, those engines blew my mind back in the day because of how 3D they were.
Like everyone I do agree Quake popularized it, I remember switching to WASD to increase my gameplay during multiplayer matches. And I remember 'strange' control methods my friends used in those days, so it definitely wasn't widespread before then.