My top 10 is always changing, but without a doubt, my favorite anime was Shin Sekai Yori. No question. It was stunningly done, in message, in animation, in writing. In my eighteen years or so of watching anime, I have never seen anything that even starts to hold a candle to SSY. It's got some really poignant eugenics and sociology lessons, and there's twists all the way up to the very last five minutes of the very last episode, just when you think there can't possibly be anything else that could take you by surprise. Great, three-dimensional characters. Great pacing. Incredible music. ("Song of Shadows" is hauntingly beautiful and amazingly atmospheric ... if you don't watch the anime, at least listen to the song. You'll thank me later.) I cannot sing enough praises about it. It blows every other anime I've ever seen out of the water.
Anohana had me crying during every episode, so I'd put that somewhere in there. Madoka Magica's art is incredible, and the style the witches are done in is fascinating, plus the dark take on magical girls ... which I've always liked because I'm not one for idyllic near-trouble-free life where the messages of hope and love feel too far away for me, as someone living in reality where aliens and monsters don't regularly appear and require me to defeat them with the power of friendship, to relate to. And there are a lot of anime I've enjoyed for their settings, or their messages, or the style they're told in. However, nothing ever made quite an impression on me as SSY. So that's the only one I'd one hundred percent for sure put in a top ten.
Everything else is childhood nostalgia, or didn't leave enough of an impression, or I only really liked one aspect of it.