Cristiano Ronaldo is a great club player. He has garnered every accolade including FIFA world player of the year and Man U's first Ballon d'Or winner in 40 years. In comparison, his national duty so far has been pedestrian by his own standards.
There appears to be a pattern. Very good performances into the lead up to the tournament where he tends to then play with a very marked "carry the team on the shoulders" quality that proves detrimental.
He came to the 2006 World Cup with the second best tally in the European qualifiers but gained notoriety for his extra curricular activities on Rooney. His actual contribution was just a PK goal against Iran. Again in Euro 2008, he scored a total of eight goals as David Healey stole the show in the qualifiers but apart from the match against the Czech Republic, where he scored a goal and assisted in the two others he did very little of note in the big quarterfinal against Germany. They lost the match 2-3 on a late rally.
So far his performances in the 2010 World Cup qualifiers have been very dull. 270 minutes of nothing. Portugal have struggled with three goal less draws against Sweden and Albania. This from a team brimming with attacking firepower like that of Ronaldo and in a group from which they should easily qualify. A note here, Ronaldo was captain of these three matches and he has not scored. It appears as if Carlos Queiroz is burdening the Man U winger.
I have to say, his performances are an inversion of another left winger, Lukas Podolski whose Bayern Munich career is pretty checkered but his national output has been outstanding.