Of the big hubs in Europe (LHR, FRA, AMS, CDG), I find CDG the worst, although I cannot completely pass judgment on as I have not yet used AMS (although many suggest that it is the best). But to call it one of the world's worst airports is a major overstatement.

If you haven't been in some developing world airports with crumbling infrastructure, poor lighting, massive crowds, no air conditioning, and incompetent staff, you just can't say this.

CDG 2 (I haven't been in CDG1) has light, food you can eat, bathrooms that were cleaned more than once in the past century, and some semblance of signs to help you.