Because I believe la Liga is a more open league in terms of scoring goals giving players like Ronaldo more opportunities
Where as the prem is a tighter league - during the winter moves especially the games get heavy and close and scoring isn't as high - hence why no one has ever managed massive scoring in the league despite over the years having the best strikers in the world playing including Ronaldo. Teams like Hull and Palace fight to the death and make it difficult for other teams - the difference between the two leagues is clear. Playing in a more open league then Suarez I believe would score a lot more. The prem is historical lower scoring for individuals.
At the end of the day there is no right or wrong only opinions and I can only express my opinion on a player I have seen regularly over the years and rate very highly and not just because of the amount of goals he scores but of everything he brings to the pitch.
I think my biggest issue I have with all these opinions you have when rating Suarez above Ronaldo is how Messi is exempt. I mean Messi has only ever played in this so called inferior league. So why is he a star and Ronaldo not? Suarez has scored 70+ goals I a top level league according to how uefa rate leagues for golden shoe. Ronaldo has close to 300. And not all of those as a striker. Although since become a forward and not a winger his record is almost a goal a game. Anyway, if Suarez gets his wish next season and plays for a Spanish team it'll be a good leveller. Until then, as he only plays league football and not against all the best defences in Europe. I don't think he'll be top of many people that don't support Liverpool's list.