While I agree that Rosberg was at times quite a bit slower than Hamilton when the latter qualified ahead of him, it is also indisputable that Rosberg outqualified Hamilton on more than a few occasions (more than any other team-mate, if I am not mistaken). So while on average, Hamilton was perhaps further ahead when he did outqualify Rosberg and only narrowly behind when he didn't, it doesn't change the fact that Rosberg did on numerous occasions, outqualify Hamilton.
And yes, I am well aware that Hamilton faced a few issues here and there during qualifying, more than Rosberg did and that may also sway the picture a bit more in Rosbergs favor, but considering Hamilton is considered to be one of the best qualifiers of all time (he certainly holds the record in number of poles), it's all the more impressive how close Rosberg was at times and even ahead. It just puts what Rosberg achieved against Schumacher from 2010 to 2012 into better context. Yes, Schumacher was aging (although I don't buy that reasoning, I think tires and car characteristics played a more significant role vs what Schumacher was used to), but perhaps Rosberg was just faster than some here would care to recognize.