In case is the top 5 / 10 Animes that produced on 2011, here is mine:
1. Steins;Gate
Unique storyline, great voice acting, and good OP + ED.
2. Usagi Drop
Although I haven't watch the last episode, but I think it's also one of the best Anime on this year.
3. Fate/Zero
On-airing series, however everything is fine so far. Prequel of Fate series.
4. Madoka Magica
Kinda overrated in my opinion, however it's a good series nevertheless.
5. Carnival Phantasm
Another on-airing series (suppose is OVA), great comedy, a must-watch series for Tsukihime / Melty Blood or FS/N fans