I have a couple of anime I found not-so-great.
Naruto - I mean, I don't see the whole fuss about it. I started watching it 2 years ago, with my friend and we reached episode 30 and it was good. After reaching further episodes, a lot of filler episodes were introduced between story events and the story was slowing down. I don't really know if I ever going to give it another try, but yea, it remains a less than mediocre anime for me. Oh, and the voice acting, the English dubbed, wasn't that great as well. That's just my opinion, though.
Lovely Complex - You might not agree at all with me on this one, but honestly, nothing caught my attention in this anime. I mean, a girl and a guy falling in love after many obstacles and people interfering in their lives is well, a little bit cliche for me. Although I do enjoy the occasional romantic comedy settings, however this one was not one of them. To be fair, I did like the characters and they were what made me finish the anime.