I'll just copy n' paste a post of mine from another FT thread....
Comparison to One Piece: The main reason FT gets "blind" hate. Statistics showed that atleast 68% of people who watch/read FT has also seen One Piece. OP fans take one look at Ft's artwork and go "OMG Hiro's copying OP that means it it sucks! gwah go hah! Plagiarism!!" Actually, FT and OP artwork, not character design, but artwork being similar is justified. Hiro and Oda used to work together for many years and are friends. Working on the same projects for years, its understandable that Hiro and Oda has developed similar primary drawing styles. However, whats really eerily similar are the designs and backgrounds of the main FT(Natsu, Lucy, Gray, Erza, Wendy) cast compared to the main OP cast(Luffy, Zoro, Nami, Chopper, Robin).
Natsu and Luffy: Both are goofy, gluttonous morons with no sense of danger. Both are the least intelligent of their respective groups and is VERY reckless. Both has a piece of clothing that is extremely important to them(Scarf for Natsu, Hat for Luffy).
Gray and Zoro: Both men are the opposite of the main characters. Both are always arguing with their polar opposites prtrayed by fire. Both men are the cool badasses of their respective groups and seemingly has no interest in women. Both men had a run in with a purple haired woman who looks exactly like a purple-haired woman in their past life(Ultear for Gray, Tashigi for Zoro).
Lucy and Nami: Both are the main heroins of their respective series. Both are the busty fanservice icons of their series. Both desperately needed money to pay off something. Both ususally wacks/gets annoyed at the main charater for being stupid.
Erza and Robin: Both women were on an island were they befriended someone(Jellal for Erza, Saul for Robin). The islands of both women eventualy came under attack with resulted in them losing a friend(Jellal becoming a psycho, Saul dying). The escape ships in the flashbacks of both women blew up and they emmdiately left the island all alone. Both became/were outcast on their respective islands(Erza became an outcast when the escape ship blew up, Robin has always been an outcast because of her ability). Both women found a place where they belonged but "ghost from the past" came back to haunt them(Jellal for Erza, Spandam and Buster Call for Robin). Both women gave themselves up to protect their friends but their friends tried to help them anyways. After repeatedly trying to throw their friends away, both women eventually gave in, accepted their help, defeated the bad guys and lived happily ever after.
Wendy and Chopper: Both are the smallest and doctors of their respective groups(Both can heal their allies). Both are "wolfs in sheeps clothing." Small cute Wendy is a freaking dragon and small cute Chopper can turn into a giant sasquatch.
Gildarts and Shanks: an obvious one
Future Rogue and Blackbeard: Both men are represnted by black an killed and ally of theirs that was represnted by white. Both men stole their former allies' powers.
OP fan hatred of FT due to character similarities is jusified.
Characters: FT has a great variety of characters but alot of them lack depth. Natsu, the main character, has no developnment whatsoever and Laxus, a super popular FT character, had horrid negative development. Some of the villains of FT had alot of potential, but they were killed off and beaten in a very similar and repititive way.
Plot: the weakest thing about FT. Some haters say "FT has no plot at all!" and they can go suck a d#%k. FT has a plot but it was WEAK early on in the series. The only thing we knew was the dragons disappeard and Natsu wants to find one of them. WEAK!! FT finally got a good plot with the Zeref buisness in the Tenryu Island arc which is quite a distance away for those at the beginning of the series. The plot as a hole is still average at best. Its a plot that not alot of people would become invested in. A thing that gets in the way of the plot is the extreme nakam power ups. Alot of poeple finds it cheesy and predictable. It gets in the way of the drama and makes it pointless(like Wendy possibly dying from face. You could see her survivng from a mile away and it made the drama buliding up her possible death cheesy and pointless).
Final Verdict: People shouldn't get into Fairy Tail with high expectations. FT is far from perfect. Readers generally look for complexity and bash FT for not being complex(yet poeple love the s#%t out of DBZ). Ft is all about simplisity people! Simplisity over complexity. FT is pure raw entertainment. A simple happy-go-lucky action shonen with humour, fanservice and a dash of complexity here and there(not much of it though). FT is just a fun read and does what it does best: entertain. Evident by being in the top 10 best-selling ongoing manga in Japan.