I definitely wouldn't credit Unreal with coming up with WASD. They were one of the earlier games to have it as the default control scheme. WASD was common in the Quakeworld days but it wasn't the default. If you recall for Quake you even had to manually enable 'mouselook'.
Yeah, I remember being at a friend's when he set it up for Quake II and it was like a light suddenly shone down on me. It was just so *right* it was like playing for the first time. I remember getting hit by some grunt who I could not locate to save my life when it occurred to me to look toward the ceiling. I felt like Khan learning about the third dimension.