[Kaijo]

There are a variety of reasons for me, of which sergel has mentioned a few. In no particular order:

#1. Equal balance of powerful males and females. Most shonen is 90-95% males who do the fighting.

#2. Natsu, while being the main male, is not the most powerful. It's a refreshing change of pace. It kinda goes well with point #1 above, since Erza can kick his ass.

#3. The other characters aren't useless! It's annoying to watch Krillin get pwned over and over, and how no one but Goku can ever really defeat anyone. And sometimes, who defeats the main bad guy of the arc isn't Natsu (or he isn't the focus), but someone else.

#4. Multi-people fight; it's not "one-guy-with-sword vs. one-guy-with-sword" over and over, repeated ad nauseam. It's got some variety, and while there is some element of power level in play, it's not directly referenced and *can* be overcome with smarter tactics.

#5. Lack of training arcs. Always a pet peeve of mine, where at least half the show is training the main character training to get stronger. While okay in small doses, I'd rather get more interesting story instead.

#6. Humor. Practically every single character has a quirky trait, and they play well off each other. Even in serious situations, some amount of humor breaks through. Some times it's not enough to make me laugh, but I do find it amusing.

#7. The music. Fairy Tail's main theme, and the slow version of it, are among my favorite pieces. They give the anime a fairly epic feeling whenever they play.

There are probably more that I can't think of, off the bat, but those are the main ones.

Edit to add: #8. The mysteries. It's not a simple series of shonen fights, nor does it have so many things that it requires a complex chart to keep track of. But we can see a larger plot being woven together in the background, from all these arcs we've gone through.