Seems like Shingeki no Kyojin is the best anime of the year for many, myself included. Well this pretty much looks like my top 10 anime of 2013 so far:
1 - Shingeki no Kyojin
2 - Toaru Kagaku no Railgun S
3 - Kimi no Iru Machi
4 - Suisei no Gargantia
5 - Chihayafuru (Season 2)
6 - Mondaiji-tachi ga Isekai kara Kuru Sou Desu yo
7 - Ore no Imouto (Season 2)
8 - Da Capo III
9 - The World God Only Knows - Goddesses Arc
10- Bakuman (Season 3)
NOTE1: List might change since I haven't seen most of the new anime series that just finished airing are about to finish airing like Kill la Kill, Arpeggio of Blue Steel, Sekai de Ichiban Tsuyoku Naritai, etc. For ~12-26 episode series, I always wait until they're fully aired because I prefer to watch all episodes one after another.
NOTE2: Not counting anime that aired in 2013 but started airing in 2012 or previous years, like Fairy Tail, Sakurasou no Pet na Kanojo, Robotics;Notes, Naruto Shippuuden, One Piece, etc. I only counted the animes series that started airing in 2013.