I am not convinced Ronaldo is a better all round player than Zlatan at all. Don't forget that Zlatan has won the league title with every single club he has ever played for.
He's pretty all around excellent. I was fortunate enough to see him at Le Parc once. I was pretty impressed. He's got power, pace, and size, but he almost doesn't need them. He's such a finesse player.
Ronaldo is a great player, no argument there. I don't necessarily think any of the big 4 are better per se, they all have different strengths and weaknesses.