The anime was adopted from Hiro Mashima's popular shounen manga Fairy Tail and it's one of those few mangas which remained loyal to its genre. The plot of the anime is set in Fiore, where mages train day and night to be the strongest magic user in the realm and join magic guilds to take on missions. Fairy Tail is Fiore's number one guild and is hated by their government for its destructive - and sometimes idiotic - members who just drink and party all day.
The anime, instead of portraying a single protagonist, follows a team of mages. The main character is Natsu Dragneel, who uses Fire Dragon Slayer magic and is looking for a dragon named Igneel. Along the way he meets Lucy, a stellar spirit summoning mage and together they team up with Gray Fullbaster (an ice mage) and Erza Scarlet, an S-Class mage (high ranking, dangerous missions mage) and one of Fairy Tail's best.
The thing I liked most about the anime is its variety in the arcs. Every single arc in the anime is extremely entertaining and there's no repetition at all (although some of the characters just keep coming back), whether it's a rival guild invading Fairy Tail or going to war with a dark guild, Natsu and company is always in the centre of trouble.
The anime has got awesome theme songs and these are one of the best I've heard since the legendary ones of FMA and the artwork is fantastic. The plot has got depth and perception and it reaches to almost every character in the guild. There are a few hilarious moments between the actions sequences, the mirth of which will leave you bent over with laughter and there are enough eye candies in the anime to hold a Miss Fairy Tail competition (which they actually do).
One drawback I found in the anime is that there is no equilibrium of strength. No matter how much stronger the opponent is or how beaten down Natsu is, he always (miraculously) wins gloriously. Of course this happens in all shounen animes but in this case, it happens every single time.