Kylian Mbappe came up with the 83rd minute winner from Nordi Mukiele’s cutback but Messi was all the talk afterwards.
“I have an incredible pleasure to see him every morning in training,” Galtier told reporters.
“He is playing well and is happy every day when he trains.
“He is a player who has always had a habit of scoring a lot of goals in a season. This year he’s regaining a taste for scoring and is becoming decisive for us.
“Whether he can be the best player in the world again, I’d say yes because he’s in incredible shape and he’s well prepared.
“He has a relationship with his team-mates that makes him happy. When he’s happy, he performs; when he performs, he can reach the standards seen throughout his career.”
Messi had a below-par first season in Paris, scoring 11 goals from 34 appearances in all competitions but has been in better form this term.
The 35-year-old Argentine has already scored seven times with eight assists in 12 games this season.