All four strikers scored at the weekend to continue their blistering starts to the season with Aguero, Morata and Lukaku locked at the top of the Premier League scoring charts with six goals apiece, while Kane is not far behind on four goals.
Speaking on Monday Night Football, both Henry and Carragher agreed Aguero is world class because of the longevity of his career.
And while Arsenal legend Henry doesn't think Morata, Kane and Lukaku are quite there yet, he thinks they will all be world-class strikers given time.
"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," he said. 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."
For Morata, Kane and Lukaku to become world class, Henry insists all three need to perform consistently in Europe and at international level, not just in the Premier League.