This is a review till chapter 415 (somewhat very near the end of the Tartaros arc.
Honestly, I would give the manga a 8 or 9 until chapter 253. Cos after that, the arcs reallly succcck.....
Up until chapter 253, at least the story was more reasonable, and touching, unlike a lot of senseless actions, power-ups, plotholes and missing characters here and there later.
Story:6
Honestly, Fairy Tail is severely lacking in story. It's not that there's no story. Like Bleach, there is a main villain that keeps popping up, indirectly or directly. But in Fairy Tail's case, there are 2, and incredibly, the way they show up and disappear is absurd. The 2 strongest villains in the manga, causing overall less damage than the "regular" cliched "I want to gain power/destroy the world/resurrect the strongest evil power" villains? Yeah, this is the first time I've seen a manga featuring such villains lacking in willpower. Honestly, it is just vexing... at least in One Piece during those circumstances, there would be an explanation behind why some villains just left after completely defeating the protagonists. In Fairy Tail? Nope no way. It's like it is logical for the strongest villains to leave the protagonists after just "defeating" them. Which is rather vague, since the protagonists seem to be stronger after begin injured, more than when they were at the start (in EVERY difficult battle).
Another thing is the MIA and illogical appearances of some characters. Like for example, after chapter 253, some character appears out of no reason, and later disappear as well without reason.
I think one of the most absurd things about the story is how the guilds and dark guilds are associated with each other. For example, 3 guilds in an alliance fight the light guild(s) one by one, out of which, 1 of them fought against a TEMPORARY alliance of light guilds. Interesting right? What the hell is an alliance for if you guys just fight one by one?
Art:9
The art is really good, and the saving grace of this manga. Consistent, clear and the character designs are mostly unique.
Character:5
The quality of the characters is largely debatable. On one hand, most of the characters' personalities are relatively consistent. On the other hand, there are a lot of weird inconsistencies in the appearances and disappearances of minor characters.
And especially with the power-ups of the main characters, and some villains, it is actually quite painful to read all chapters up to 415 in one go. It's like the author forgot what did some minor characters behave like, or even it seems like he forgot they existed.
Another flaw is that some characters which become main characters changed a bit too much. Pretty much like the spell which turns villains goody-goody, but without the spell.
Enjoyment:8
Till 253 it is a 10, then till 415 it is a 6. I think this pretty much sums up the enjoyment level for the manga. It has much to do with the direction of the comedy and fanservice before and after 253.
Overall:7
If shounen, adventure, action and friendship is what you dig for, look no further. Oh yeah, it's rather of a fantasy genre as well, so make sure you enjoy over-the-top power-ups when reading this manga!
P.S. This would be a fantastic example of power creep in games.