R is interesting in that it has one library which has zero real competitors to the point where it becomes a justification for using the entire language: ggplot2. It's almost like ggplot2 crosses over from a package to an application, and R is the user interface. Any examples like this in other languages? I can't think of any, maybe Python & scikit-learn 5 years ago.
Can you compare ggplot2 to matplotlib? 90 seconds of googling didn't seem to indicate to me that ggplot2 is particularly different, either in terms of its power or expressivity, than matplotlib.
Those 90 seconds of googling constitute my entire knowledge of ggplot2.
From people that have used both extensively (which does not include you or me, it would seem), I always hear that ggplot2 is unsurpassed. Admittedly, that isn't a satisfactory answer to your question.
