Courtois is currently on loan from Chelsea to Atletico Madrid for the third consecutive season.
Alderweireld feels the 21-year-old should make his move to Atletico permanent or move elsewhere.
"He is very smart and I think it would be a good choice for him to maybe stay with Atletico, or go to another club where he will be number one," Alderweireld told Sky Sports.
"He does not want to sit on the bench for eight games then play for one.
"I don't think he has a weak point and I think he can be the best keeper in the world. He is good with the ball, he is good with his feet and he is great on his line.
"I see him in training every day and I see him in games and I doubt there are any keepers better than him."