Riyad Mahrez opened the scoring with a low shot past Orjan Nyland after 18 minutes.
The Algerian doubled City's lead six minutes later before Aguero fired in from 20 yards to make the score 3-0 after 28 minutes.
Gabriel Jesus guided in from a superb Kevin De Bruyne pass to cap a stunning first-half display.
Aguero scored his second on 57 minutes to overtake Thierry Henry in the scoring charts with his 176th Premier League goal and lashed in to complete his hat-trick with nine minutes remaining.
The Argentinian's 12th Premier League treble surpasses Alan Shearer for the most hat-tricks in the competition.
Villa's Anwar El Ghazi grabbed a late consolation from the penalty spot.
City are second with 47 points, 14 behind leaders Liverpool having played a match more. Villa sit 18th on 21 points.
Aston Villa: 18 Jan v Brighton (A)
Man City: 18 Jan v Crystal Palace (H)