What makes a good phycological anime/manga?

A good psychological anime to me would have to be something that really makes you think. I also think it needs a good plot and some 'thrilling' moments. Rather than focusing on physical/external conflict like in 'fighting' animes, the psychological genre should focus on anything relating to the mind, like a mental battle between characters or a character resolving things in their head.

I like psychological thriller anime the best. I don't need to give any examples because MidnightTokyo47 already listed some good ones from that genre. ^^

Death Note
Big O Roger
Gantz
Welcome to the NHK!
Elfen Lied
When They Cry
Ghost Hound
Ergo Proxy
xxxHOLiC
Monster
Neon Genesis Evangelion
Mawaru Penguindrum
Requiem From The Darkness
Ayashi no Ceres
Chaos Head
This listahan was from an anime site called justdubs.tv