According to him, he has a long way to go before reaching the standards set by Ronaldo, who just re-signed for Manchester United.
Ronaldo scored his 111th goal for Portugal this week to become the all-time men's scoring charts.
At age 28, Lukaku has netted 66 times for Belgium, giving him an outside chance of eventually catching Ronaldo.
But, speaking at a press conference ahead of their World Cup qualifier against Czech Republic, Lukaku said: "Don't ever compare me to Cristiano Ronaldo, never."
"Cristiano Ronaldo is, for me, in the top three best players in the history of football," he continued. "I'm not going to rank him from first to third but he's in there.
"What he has achieved in football today for players of my generation is something exceptional.
"I was lucky enough to play against him in Italy and now that he's back in the Premier League, it's all good for English football.
"As for the rest, comparing statistics and all that, it's useless."
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