Van Basten played in all 4 Netherlands games in Italy '90 and was very underwhelming. Then he played in all their games in Euro'92 and not only failed to score a single goal but missed a crucial penalty as well. In other words, he had 8 consecutive games without a goal at big tournaments. All in all, he scored 5 goals in 13 games in big international competitions. That's unimpressive for a CF.
Van Basten was one of my favourite players when I was growing up but Ronaldo is better and it isn't even close. The only thing that Van Basten has over Ronaldo is elegance. He was a more elegant and aesthetically pleasing player (when at his best). He had a magnificent right foot and was a fantastic header of the ball. But so is C. Ronaldo. Ronaldo is a more complete forward though: unlike Van Basten he is two-footed, very quick and dynamic, far more athletic and hungry, could play any forward role (winger, CF, SS), contributes much more outside the penalty box, is a better dribbler (in his early 20s), is better at set pieces and is far more productive. Van Basten wasn't an exceptionally prolific striker. His numbers in Seria A in his prime (89-92):
19, 19, 11, 25.
That's nor particularly great even when one takes in consideration the fact that Seria A was a very strong and defensively minded league. Why? Because he was outscored in some of these seasons by forwards like Serena, Vialli and Signori who weren't exactly world beaters. Signori scored 26 goals in 1993 and that's more than Van Basten ever managed in Seria A. Actually, Van Basten scored only once 20+ league goals in Seria A. Needless to say that C. Ronaldo would have shit on Serena and Signori big time.
Again, it's not close at all. Ronaldo is in a different league to Van Basten. If Van Basten had a rival like Messi back then, he wouldn't have won 2 let alone 4 Ballon d'Ors. (Maradona wasn't eligible for Ballon d'Or.)