That ranks is the week sales Munsu. Volume 27 of the manga sold about 230k copies (adding normal and limited edition) as a new release. It did fairly good on that week... but if we scroll down and see the Naruto volume it has 80k sales that adds up to 800k. One Piece ain't there, but it usually sells over a million.

So yeah... Fairy Tail is popular, but its nowhere near the popularity of the 'Shounen' from Shounen Jump.