Boateng, who played with City last year, saw Italy striker Balotelli defeat his Germany this week.
Boateng, who signed for Bayern Munich last year, said: "Balotelli, in this form, is a world-beater.
"People talk about all the controversial things he does but when he's focused he's unstoppable.
"We didn't underestimate him, we just couldn't cope with him. He just took us to pieces.
"He's frightening. Considering his age and the talent he has he's more than capable of becoming one of the best strikers in the world.
"In this tournament he has undoubtedly proved there are few strikers that can live with him."