The closest to being world class, or is world class, or has been world class is Aguero because of the longevity of what he has done in the Premier League year in, year out," Henry told Sky Sports.
"He's won the league here and got to the final of the World Cup. He's been doing it the longest so you have to give him a bit of credit.
“I think we sometimes bypass Aguero like he didn't happen but we all agree that stats show he's the best.
"The other three, they will be [world class] but they are not yet. Lukaku has only just arrived at Manchester United and he's not played in the Champions League.
"We always talk about world class and the debate is always there, but Aguero is the closest to it.
"The others, I have no doubt will be. Kane himself said he's not in that bracket yet because of the reasons I mentioned.
"We should be happy to have these guys in the Premier League."