Based on the erotic manga by Akazawa Red.

Why is Fairy Tail anime so popular?

Hmm, not sure why it’s popular with others but for me it’s the characters and the combat.
In Fairy Tail it never seems like there’s overshadowed characters, everybody gets their screen time and everybody has their own moments sometimes. Most anime with big casts don’t seem to do so well in that aspect, or anime like Dragon Ball wind up having background characters that don’t really do much while the show revolves mainly around Goku and Vegeta now. Anyways back to the characters, there’s just so many likable ones.
Natsu, Cona, Lucy, Happy, Erza, Juvia, Gray, Elfman(BE A MANNNNNN…It’d be funny to see a conversation between him and Armstrong from Fullmetal Alchemist), and so on. The plot..I’ll state it the way I’ve seen others say it, the arcs aren’t very which in a way that’s pretty good.
Things don’t get drawn out and lost in some slower or not as interesting moments that might occur in other anime.
They’ve had some pretty neat storylines here and there. As some others have mentioned, the music’s pretty good. Like how does one not hear stuff like that and not get pumped? Lol What I like about it is the comedy.
I can’t recall an anime that’s made me laugh as much as FT has, well cept maybe for One Piece.
I remember one time when Lucy lost her clothes because one of the dragons took away her dignity, or essentially just made her clothes disappear, and she got shot off towards Natsu.
Her and Natsu wound up getting stuck in some bell that got knocked off around the area they were in so when they finally landed and got out..Natsu was making fun of her for being naked. He was saying stuff like the Guild’s resident flasher and I lost it when he called her Lucy HeartFeelmeUp haha.
FT fans probably know what I’m talking about.
Probably one of the funniest imo is when Erza and Jellal had a moment and Ezra was standing there reflecting on it after Jellal had left.
Happy, being the smart little cat he is, tried to troll Ezra about it and well..You see how it went over for him I wouldn’t be surprised if Happy wound up on the moon after that one. And on to the combat.
Fairy Tail has some incredible fight scenes imo.
In anime like Naruto, Dragon Ball, and such you mostly just seem the main characters become the only real relevant ones in combat as the series goes along whereas in Fairy Tail it’s like everyone shines.
Sure, Natsu, Gray, Erza, Laxus, and such are the more powerful members of the guild..But like I said, almost all of the characters get their times to shine.
Cona’s done great in battle, Lucy with her spirits, Wendy’s held her own, Mirajane is a force to be reckoned with, and so on. It’s like it’s refreshing to see that variety in battle because it feels like it’s not only up to the strongest like Natsu and such to save the day but a combined group effort prevails. Fairy Tail might come off as a little generic, but imo it’s good enough that when you watch you want to keep watching because there’s just something about it that entices you, or at least that’s how it is for me.