Just to put things into perspective:
Giggs has 30 assists in the CL.
Robben, who is 30 now, has 13.
Xavi has 17
Figo has 10 (Nani too!)
At 27 goals, there are no wingers that have more goals than he does. So much for the not scoring goals as a winger. There are no wingers who have scored more goals than Giggs in the PL (there are central midfielders who have).
When I say contribute to the team, why talk about the utmost top level a footballer can reach? Are you talking about a season, a month, one game? If you are talking about one game, I would almost be tempted to put Giggs ahead of Ronaldo. For top level consistency, Giggs isn't up there with Ronaldo, Messi etc, but for quality and contribution over a career, very few can better him. So who would you want? Robben who has put in a few good years but at least as inconsistent as Giggs ever was?
Of course, Giggs has more games than any other player in the CL and the EPL. However, do you think he got those games because he has a hairy chest? He got them because he delivers time and time again, even when people have written him off. BTW, he only has 8 more appearances than Xavi and has almost twice the assists. Then we all know that Giggs has contributed in many more ways than just assisting or scoring, maybe not to the extent that Xavi does, but more so than most wingers. Saying he hasn't scored enough or been productive enough is ridiculous, imo.