His work ethic may have been questioned by manager Jose Mourinho last season but he has turned into one of Chelsea's most important players this term.
The Belgium hot-shot has found the back of the net 11 times this season while providing six assists in Chelsea's dominance at the top of the table.
"On his day, nobody can stop him. He has such great quality on the ball; he can create something from nothing and that is a sign of a special player," Henry told Sky Sports.
Mourinho said: "He was a kid always living on his amazing natural talent but from a certain moment he started to have some tactical education, some mental education.
"He is already a top player and his evolution has been fantastic.
"He is still very young and he can become the best player in the world."