Fairy Tail isn't part of Weekly Shounen Jump, hell, it's not even a part of jump so it can never be an official 'Big Three'.
Aside from that, people seem to use 'good' and 'entertaining' interchangeably, generally things that are good are entertaining, although sometimes only to a specific audience, but something entertaining isn't always good. Imo FT can be entertaining, but the only thing good about it is that it can entertain.
Think of FMA, then think of Fairy Tail, then think of FMA again, get it?