both have mecha both are deep in different ways and surpass the standard mecha anime
The most obvious common theme between the two is the use of mecha. The two anime have the exact same type of design for their mechas.
Both really just have the same feel in terms of themes, too.
Code Geass and Neon Genesis Evangelion are both high quality, riveting, mecha anime. Both series deal with politics, warfare, and psychology. They both discuss subjects such as human nature, the meaning of life and happiness, and sorrow and insanity. Both anime have fantastic soundtracks, great voice acting, and beautiful, sharp artwork.
Both anime also contain much symbolism, some drawing its roots from religious symbols (although this is much more prevalent in Evangelion).
Both of these anime have very memorable characters and great development.
*Both are highly recommended.
It's related do to the fact that each character running a different robot has a meaning and only certain people can use such robots and they are working for an organization to stop them.
What can i say about these anime!
Epic plot, amazing characters, memorable moments...
Masterpieces that everyone should see.
Mecha, action, drama,...
They both have Giant Fighting Robots and hot girls.
Both are a coming-of-age story following the development of a central male character; a battle to save humanity/society from a menacing group of marauding giant monsters
The deconstruction genre is present in allot of anime for primarily short periods of time.
Code Geass has allot of elements and feelings that represent Evangelion in a few ways. Although, the protagonist differ from one another, both Evangelion and Code Geass come very close in the long term for just general deconstruction in the anime's themselves.
Both of these shows are excellent psychological animes. The mechas in both are insanely epic. One other similarity I found is that both have the monumental choice of accepting or rejecting God
Apart from the obvious mech aspect, they're both highly intelligent animes that are full of mystery, often doing things you didn't expect. They both have a very 'grand' nature to them, slowly moving up from a small contained world story into something that blows all proportions out of the water. Both being a ride from start to finish, they both seem to have a very well thought out story structure, as well as the occasional comedic episode to keep things balanced.