The 38-year-old five-time Ballon d’Or winner joined Al Nassr in January following his contract termination at Old Trafford in November.
Ronaldo has since scored nine goals in 10 appearances for his new club, who are second in the league behind Al Ittihad.
The Portuguese’s move came after stints with some of Europe’s elite clubs, including Juventus, Real Madrid and United, along with Sporting Lisbon in his homeland.
Saudi Arabian clubs have been linked with the likes of Lionel Messi, Sergio Ramos and Luka Modric in recent weeks as the league tries to utilize its financial wealth to grow.
“Saudi is a very competitive league,” Ronaldo said. “It’s not the Premier League, I’m not going to lie, but it’s a league that left me positively surprised.
“It has good teams, it is balanced, the Arab players are good, the foreigners give quality.
“Possibly it will be, in five to six years’ time, if they continue this plan, the fourth or fifth most competitive league in the world.”
Ronaldo is back in Portugal ahead of their Euro 2024 qualifier against Liechtenstein, having endured a difficult World Cup where he slipped out of favour in the starting XI.
That occurred amid his United exit which came to a head after Ronaldo conducted an explosive interview, claiming he was “betrayed” by the club.
“Sometimes you have to go through a few things to see who’s on my side,” Ronaldo said.
“At a difficult stage, you see who is on your side. I have no problem saying I’ve had a bad time in my career, but there’s no time for regrets.
“Life goes on and, doing well or not, it was part of my growth. When we’re at the top of the mountain, we often can’t see what’s down.
“Now I am more prepared and this learning was important, because I had never been through this as in the last few months. Now I’m a better man.”