Ronaldo, 38, scored 14 goals in 16 games for Riyadh-based Al Nassr following his January move after having his Manchester United contract was cancelled by mutual consent last November.
The former Real Madrid and Juventus forward could be joined in Saudi Arabia by former Real team-mate Karim Benzema, who sources have told ESPN will join newly-crowned champions Al Ittihad, while ESPN reported in April that Lionel Messi has an offer to join Al Hilal when he leaves Paris Saint-Germain this summer.
But despite saying he has enjoyed his brief stint in Saudi Arabia, Ronaldo says that areas such as refereeing and VAR need to improve.
"The league is very good," Ronaldo said in an interview with the SPL. "But I think we have many, many opportunities to still grow. The league is competitive. We have very good teams, very good Arab players, but they need to improve a little bit more the infrastructure.
"Even the referees, the VAR system, should be a little quicker. I think other small things they need to improve.
"But I am happy here, I want to continue here, I will continue here. And in my opinion if they continue to do the work that they want to do here, for the next five years, I think the Saudi league can be a top five league in the world."
With Benzema, Messi and other high-profile players linked with moves to Saudi Arabia, Ronaldo said such big-name arrivals will accelerate the process of improving the league
"If they are coming, big players and big names, young players, 'old players,' they are very welcome because if that happens, the league will improve a little bit," he said.
Ronaldo has finished his first season at Al Nassr without silverware due to Al Ittihad winning the SPL and local rivals Al Hilal lifting the King Cup.
And the Portugal international admits that he expected to win some honours this season following his move to Al Nassr.
"Well, my expectation was a little bit different," he said. "To be honest I expected to win something this year, but it is not always the way we think or the way we want, sometimes we need passion, consistency, and persistence to achieve the best things.
"So, I still believe that next year we will improve a lot, let us say in the last five or six months, the team has improved a lot, even the league, all the teams improved.
"It takes time sometimes, but if you believe and you think it is your goal, I think everything is possible. I expected to win something this year, but we didn't, but next year I am really positive and confident that things will change, and we go in a better way. So, let us believe that and work on that."
Ronaldo, meanwhile, said that adjusting the culture in the Middle East has been a challenge
"One example is in Europe we train more in the morning, but here we train in the afternoon, or evening and in Ramadan we train at 10 at night -- so this is so strange," he said.
"But as I tell you these situations are part of an experience, memories. I like to live these moments because you learn with these things.
"It is difficult, but it is nothing I have not seen before. My experience so far is that Saudi fans they really love football and like to live the life and it is good and I am so happy until now."