France international Griezmann initially struggled to make an impact at the Vicente Calderon when he arrived from Real Sociedad in the close-season, and it took him over two months to break his La Liga duck.
However, the forward has quickly grown into an influential player for the Spanish champions - and he once more showcased his talent with headers in each half against Lucas Alcaraz's side in Atletico's first game following the mid-campaign break.
That followed a hat-trick in Atleti's 4-1 beating of Athletic Bilbao before the break, and head coach Simeone believes Griezmann is reaping rewards for his hard work.
"Griezmann individually has been growing now for some time," he said.
"Apart from the goals, which are very important for him and the team, what I like is his hard work for the team and when he works to recover the ball.
"He can occupy other positions apart from the wing, which is where he has been playing. I can see a more complete player than when he first arrived."
Simeone also paid tribute to centre-back Diego Godin, whose 82nd-minute goal made it 3-1 and ended any hope of a Levante comeback.
"Diego is an important player who has scored important goals this season," he added.
"I hope he continues like this. He has a great personality and is important within the hierarchy on our team."
Atleti's win leaves them level on points with Barcelona and just one adrift of local city rivals and Liga leaders Real Madrid, who have two games in hand over Simeone's men.
