What's the best anime you have ever seen?

There's a lot of series I greatly enjoyed and get a perfect 10 from me but if I had to pick one that's be Infinite Ryvius. Lord of the Flies in space, with older kids(teens) with the approach of an eastern culture. what's not to like in this hot mess? :P

Cowboy Bebop

A toss-up between Rebuild of Evangelion 2.22 and Revolutionary Girl Utena.

Boku no Pico, best anime ever

Probably Samurai 7 or Basilisk.
Can't decide.

My favorites are Black Cat, Rosario + Vampire, To Love-Ru, Mayoi Neko Overrun and the fan made animes of Touhou.

Either Pokémon or DBZ, haven't seen much others.
Also I watched it as a kid, I might consider watching an anime series if there is an adult (I don't mean sexual here) mystery/thriller-ish series, but I don't know any.

Cory in the House or Sonic X

"Highschool of the Dead" and "Detroit Metal City"

Tie between Tokko and Claymore

Trust me . watch high school DXD

Move aside peasants. Evangelion master race elitist have arrived <3

Steins:Gate.

One piece, the long and the good

Evangelion or FLCL, I'm still undecided

Danganronpa was the best in my opinion. I mean that's how you should make an anime from a visual novel. Monokuma was a really good character in my opinion uppupu
I really liked Persona 4 The animation too, it was a nice recap after 98 hours in Persona 4 Golden.

I really enjoyed watching staint gats and kuroko no basket but FMA brotherhood is my favorite

It's really hard to pinpoint "The Best". There are so many genres of anime, pursue different things, ,aking different points.
If we're talking the best as "most perfectly made" it's probably Mahou Shoujo Madoka Magica. That thing just leaves an everlasting impression on you.
If the best as the one that made you feel the best, it's Great Teacher Onizuka. It's the most upbeat thing in the world.
If the best as "The most AWESOME", then it has to be Tengen Toppa Gurren Lagann.
So, is any of them better that Ghost in the Shell? Is any of them more fun that Kill la Kill? Is any of them "more good" that Haibana Renmei? There are a lot of other good anime's that you may like more, because we're all different people.

The first full metal alchemist (loved it)
and full metal alchemist brotherhood

I consider dragon ball above all else, out of every chart :3

There are still a lot of animes on my list that I want to watch, but so far the two animes I enjoyed the most were Kokoro Connect and Chuunibyou demo Koi ga Shitai!.
Yeah I'm such a romantic guy :3 xD

That's really hard to answer. Some anime have really great stories but terrible voice acting or something about the animation is just off. Some are the reverse.

As a kid, I grew up watching Dragon Ball and Sailor Moon. Somehow I got into Series Experimental Lain and .hack//SIGN. I loved loved LOVED Studio Ghibli's work.
Sadly, I was more into reading manga than watching anime so overall I can't really give recommendations over the board, but I do recommend watching Psycho Pass and Puella Magi Madoka Magica.

Code Geass.

Higurashi is good but my favorites are NGE, Akagi and Cromartie.

The best would be Akira. I have a VHS copy somewhere in my house that I got from a rental about 10 years ago with the original english dub:D

For nostalgic reasons Moomin (with Swedish dub) will always be #1 for me, but if not counting that one, the best anime I've seen must be either Clannad or Samurai Champloo