Rah Xephon is often criticized for its similarity to Neon Genesis Evangelion, with some anime critics going as far as to call it a ripoff of Evangelion. But I think this characterization of Rah Xephon is unfair. The anime sure does have a lot of stylistic similarities to Evangelion, to be sure. If you're a hardcore Evangelion fan like me, it will be impossible not to notice the many similarities of certain scenes, shots, concepts, and character designs.
But Rah Xephon, if you look beyond the surface similarities, is a completely different, and in some ways, better, anime than Neon Genesis Evangelion. It has a more mystical, surreal feel to it. The characters are more likeable and spend less time bitching and backstabbing. The protagonist is more heroic and mature, without being insensitive or too perfect. And yet, it feels every bit as artsy and psychological as Evangelion. It truly is a beautiful anime.
One thing unique in the genre for Rah Xephon is how important music is to the combat. The fighting is not brutish violence, but is about "tuning the world", fighting with music. There is a deep sense of ancient spirituality to this kind of fighting.
Manga by Takeaki Momose
Novel series, game, OVA
While this anime has stuff you've seen before, and doesn't have a very original plot (oh gee, another teenage boy has to pilot a giant mech and save the world), it is emotionally evocative in a very beautiful way. It's kind of like Vision of Escaflowne for me in that respect. I would recommend it for Evangelion fans who want something like Evangelion, but less depressing. Ultimately, it has less pain and sadness than Evangelion, making it also a good show for people who didn't like Evangelion because it was too dark and cynical. There is more hope in this anime, and more of a pre-industrial spirituality that's very romantic and emotionally appealing. If Evangelion is about a humanity that lost its soul, Rah Xephon is about humanity finding it again.