Hell, if philosophy is the driving factor for a good villain, then GladOS wouldn’t even be on your list. A villain doesn’t need to be morally grey to be a good villain. Plenty of good villains are evil just for the sake of being evil. Even GladOS would fall into that box.
The point was simply that players need an end goal to keep them focused, and having a consistently present villain acts as a moving end goal. The player is driven to chase that goal until the conclusion, because the villain is always just out of reach. If you see a goal waiting on the horizon, the march there feels like a slog. But if the goal is consistently at your fingertips as you chase it, you’ll chase it all the way to the horizon without even realizing.