When do we ever see the "commander" on xcom game?

You have this screenshot right on the wiki page you linked showing the Commander before the final mission.

the Commander

You see the commander in a similar suit during the rescue mission Operation Gatecrasher. It's intended for the person to be obscured by the suit to allow your imagination to fill in whoever you like, as the Commander is your personal avatar in the game.

Note, that you only see the Commander in XCOM 2, not XCOM: Enemy Unknown.