Let me ask a very simple question. Who is the best footballer, so far in 21st century? My answer would be Cristiano Ronaldo. Some may go for Lionel Messi, and Kylian Mbappé may be the choice for a few others. Then there will be significant support for players such as Luka Modrić, Zinedine Zidane, Thierry Henry, Andrés Iniesta and Xavi Hernández. Out of all these players, how many are participating in the Saudi Professional League? Only Ronaldo. And that makes him the best player right now in this league.
You make the question as SPL is the best league in the world, when it's not. That makes the question you asked flawed. I like Cristiano without hating Messi & I personally think Cristiano is the best player in the world regardless of whether he has the WC trophy or not. It's because of his hard work in this industry, it's not easy to be like him where he can maintain his performance, today he's an icon for the football industry.
Anyone disagree with my statement?
Read my post carefully. I never said that the Saudi Professional League is the best league in the world. I was saying that at the moment, Ronaldo is the only world class player who is participating in SPL. Hopefully in the future they will get someone like Mbappé or Messi to participate in this league. Afterall, at the most Ronaldo has 2-3 years of career left. They need to make sure that the new audience remains with SPL. One of the ways to do that is to bring some of the well known stars from Europe.