Are you basing that on that one game? Because Ronaldo's had a better season that Kaka, and the two R's have three/four years on him.
Nah I never do that, I'm basing it on overall talent. Ronaldo has imo been the best player this season, but Kaka has been fantastic in a ordinary season for AC Milan in the league where they have struggled until recently to find goals as Inzaghi is injury prone, Oliviera cant handle Serie A and Gilardino is Gilardino. His 9 goals in the CL also show that he does it frequently at the highest level.
He may not have scored many goals in the league this season, but look at his perfomances hes easily been Milans best player, he pretty much runs the team. Seedorf has been poor this season, Gattuso doesn't attack much so its basically left for Kaka to carry AC Milans attacks, and now he has Ronaldo who can actually score goals, AC Milan are now frequently using the Kaka and Ronaldo combination, and its working well as they have only lost once in the past 10 games in the league (vs Inter).