Brazil and Belgium will clash in Kazan for a place in the World Cup semi-finals and much of the attention will be on the world's most expensive player.
Mexico coach Juan Carlos Osorio labelled Neymar an "actor" after his reaction to having his ankle stepped on by Miguel Layun during their last-16 clash, but Lukaku is a big fan of the former Barcelona star.
When asked whether he sees Neymar as "skilful or an actor", Lukaku told reporters: " Skilful. To me he's not an actor.
"Players who play against him are tougher because he has quality that is out of the ordinary.
"I think Neymar in the future will be the best in the world and I'm happy to be playing against him for the second time."
Lukaku's coach Roberto Martinez highlighted Neymar's ability in one-on-one situations as something his team will have to pay close attention to, but he feels Belgium also have plenty of "individual talent" to cause significant problems.
"We respect immensely Brazil and Tite, the work he has done," Martinez said at the Kazan Arena.
"The games aren't for coaches, they're for players, you have to help the players be themselves on the pitch.
"We look forward to that. Individual talent is a big weapon of both teams, we rely on one-on-ones, being able to score, open-play football.
"We aren't a team that relies on being defensively strong. You have to be perfect defensively but we rely on what we do on the ball, the same with Brazil.
"In that case Neymar is a big exponent of that, a technical footballer who's decisive in one-on-ones.
"We have to be aware of that, keep him quiet and we can allow our players to have a bigger role in the game.
"A lot of respect, you 'll only get respect for Brazil from Belgium for what Tite is achieving with his team."