N'Zonzi joined Stoke in the summer from Blackburn Rovers and has been one of the club's most impressive performers so far this season.
He added: "If he keeps improving, he can play for any of the top four or five teams. He's very good in the air, his mobility is excellent as well and it is just getting him more disciplined in the team structure.
"We also feel he can score more goals. He's been outstanding for us - one of the best signings we've made."
The Potters travel to Upton Park to take on Sam Allardyce's West Ham on Monday night with N'Zonzi expected to start.
Allardyce worked with N'Zonzi whilst at Blackburn and it was the Hammers boss who first brought the midfielder to Pulis' attention last year.
"Sam had worked with him and said we should get him if we could," added Pulis. "That was 18 months ago.
"I didn't ring him this time as I didn't want to alert him. Sam felt he will be a top player who hasn't realised his potential yet. But I think his move for him was being blocked because of his relationship with Blackburn at the time."
N'Zonzi's form has alerted both France and Congo who are battling to secure his services, but Pulis is hoping that he picks France to ensure he is available for Stoke during the Africa Cup of Nations in January.
"I'll leave the international stuff to Steven, I think when nationalities come into play you have to leave it to the international to decide," said Pulis. "But if he picks Congo, I'll never speak to him again!"