Aldnoah.Zero, Mobile Suit Gundam: Iron-Blooded Orphans Recommendations
They both have giant robots that are special or unique. They both have a very solemn, monotone, cold main character who are able to drive the robots better than anyone else. Both have a princess from Mars who comes to Earth for political reasons. Both have people who are trying to kill or capture the princess for political reasons. There's war related history and events. People die. People fight. Both have many characters from all different backgrounds that some how add to the story.
Seriously, there are both so similar I'm surprised no one had already suggested them.
A young lady who is an important political figure from Mars, wants to travel to Earth for the betterment of humanity. On her journey she is aided by young people who are brilliant in mecha-fighting, specially the main protagonist who is a calm-minded person and head for the battles without the slightest sign of hesitation or frightened look. Events change and take a surprising turn when the people from Mars betrays the lady, and battle breaks out between our protagonists and the Martians. A lot of deaths occur in these strategic battles as political turmoil among them take a turn for the worse.
Both are Mech that deal with political problems. Both deal with Mars and Earth. The main character is also stoic in both but are combat geniuses.
Hanae Natsuki is in both, but he's not a main character in Gundam, even though he has a pretty major role.
* Child soldiers...
* Both sides uses huge robots/mecha's as the main weaponry...
* Both MC's are combat geniuses....but like every other geniuses they're a little bit cold towards other characters...
* Both have enemies who are trying to kill or capture the princess for political reasons.... (independance)
* Both have really emotional moments at times...
I feel those have the same type of ridiculously powerful, cool main character, taking care of the bad guys while his comrades get slaughtered. Also realistic mecha with suits needing refueling, ammo, and repairs; that goes without saying for gundam. Good looking battle scenes being only a background for greater political schemes and power struggles. Obsolete and forgettable romance threads shoujo style. Gundam gets a lot more character development.
The plot line in both of these shows is nearly identical. However the way the plot progresses and the way the story is told is quite different. Both revolve around a interplanetary society where the higher class of one planet considers those from a different planet to be inferior, despite the fact they are of the same species. In MSG Iron-Blooded Orphans the higher class of Earth amounts that the people on Mars are worthless, and many children are enslaved and forced to fight. In Aldnoah.Zero the ruling class on Mars considers the Earth to be inferior. Both shows involve a Princess traveling to another
Both shows are gundams about Marsians vs Humans. They have very similar plots if you enjoyed one then you will enjoy the other one