What's there to appreciate about Fairy Tail? It's fairly shallow.
Honestly, it's biggest flaw is in how the plot is
executed. The story itself is actually pretty interesting and unique but the writing is really poor which results in the show often axing its own suspense or tension, making plot twists really obvious, undermining what should be major moments for the story or individual characters etc which makes the whole thing seem a lot more shallow than the content actually is and absolutely obliterates the emotional weight some of it could/should carry. Also it has the worst filler arcs of any series ever.
There's definitely positives in there though. The world itself is quite interesting and while not perfectly displayed to the audience, we come to know it pretty well through showing and telling. For example, we learn how technology is quite a ways back from where it is in the real world and is built around magic instead of physics and chemistry for the large part and by extension how integral magic is to their society despite only a small percentage of people being naturally magically gifted.
Another strong point is the characters. Not Natsu obviously because he's basically carefully formulated to be the textbook shounen protag (although I would argue he's actually a better character than fellows Luffy or Goku by some margin). I'm talking about the other main cast and the supporting cast. Although not as prevalent as I'd like by any means, there is actual character growth present within the cast. In particular Wendy, Laxus, Carla, Cana, Ultear, Jellal, and Gajeel (I'll spare listing every character with notable growth) all display pretty decent growth and to a lesser extent we do see growth from Gray, Erza and Lucy. Where character growth is missing, there is often at the least a decent degree of character depth too which is where the latter three characters excel more. What's really impressive though is that even though the cast of characters is absolutely enormous so many of them feel distinct, interesting and likeable. The antagonist side of things is weaker in honesty, but even there there's been some compelling or well-conceived of villains. Fairy Tail also has to get a shout out for how it treats female characters. The fan-service is fucking infuriating at times but unlike most shounen series FT doesn't shy away from creating strong, relatable and relevant female characters which is a nice change.
It's definitely no master piece and could be a
lot better than it is, but I am forced to admit my original prejudices, although not entirely unfounded, were largely wrong. It's a decent show and much better than I was originally willing to give it credit for. As far as shounen goes I'd rate it higher than DB and One Piece easily.