If you're looking for anime similar to Majestic Prince, you might like these titles.
The universe of the future is divided between the Earth Alliance and ZAFT. After a year of war, ZAFT attacks the neutral colony Heliopolis to steal five prototype mobile suits. The mission is a success, but a young man named Kira stumbles upon the fifth Gundam, and he may be the Alliance's only hope...
Both of thse shows are about kids joining the military and learning to pilot giant mecha suits in space. The animation/character designs are very similar, and the overall feel of the shows are the same. If you enjoyed one, you'd no doubt enjoy the other as well.
I have to say... The overall feeling I had watching both anime is the same, they are both incredibly good mecha anime. I will recommend both anime to anyone who likes either and if you haven't watched any of them start with the classics (just saying). Back to topic, they are both mecha anime who star teens fighting a war in MSGS you see action on earth and outer space and in GKMP you see more action in space. Like I said, overall feeling, it's almost like one was inspired by the other.
Far, far away in a distant time, there is a tribe of people called the Golden Tribe who have the ability to create stars and foretell the future. They gave out a warning to those who have yet to mature: 'Move.'. Three tribes answered their call: the Silver Tribe, the Bronze Tribe, and the Heroic Tribe. Soon after, the Golden Tribe encountered a crashed ship in which only a baby human known as Age survived; they named the child's race the Iron Tribe and assigned one of the few living members of the Heroic Tribe to protect him and his race. Now, in a distant part of the galaxy, humanity is threatened with extinction at the hands of the other tribes. With only a prophecy to go on, they set out to the deepest depths of space to find their savior named Age -- humanity's last hope.
If you like the unique character designs of Hisashi Hirai, you will like Heroic Age if you also like Majestic Prince.
It is the year 2356 AD, 189 years after a shockwave from a distant supernova decimated the Earth. Since that fateful day, humanity has begun training for a final mission to protect the planet from the inevitable oncoming 2nd shockwave - a mission whose failure means the annihilation of mankind. For Katase and her friends, their training at the foundation Stellvia is just the beginning of an adventure that could lead to saving the world, or seeing its end...
These two definitely have a different tone - Stellvia focuses more on the school life aspect of the space cadets (with occasional alien fighting), while Majestic Prince focuses mostly on the alien fighting. But if you liked the 'kids thrown into space battles' aspect of Majestic Prince, and want something far superior on all levels (including character design and story), check out Stellvia.
In the distant future, aliens called Victim destroyed all the worlds of humanity except for Zion. In this desperate time, young boys of the space colonies are sent to GOA to learn how to, and compete for the right to, pilot the fighting machines designated as Ingrids. These child pilots are assisted by EX -- a special power, and by female partners who repair the Ingrids. However, to save humanity, exceptional candidates are needed, and two new students, Zero and Hiead, motivated by their desire to succeed and burning rivalry, may be the human race's last hope...
When the oppressive Kingdom suddenly conquers the planet Kibi, a group of space cadets are stranded aboard the spaceship Amaterasu. With no money or power, the crew is funded by the Space Channel TV station… for a price. For though they are given the money to buy the Amaterasu and battle the Kingdom, Shinon and the rest of the cadets must also become reality TV stars, allowing the network to dictate how they look, how they fight, and how they react when faced with the horrors of death. For the cadets aboard the Amaterasu, the battle has just begun...
I fully admit this isn't the most solid recommendation, I just thought of the pairing immediately because of one rare aspect shared between the two: battles and machines that are funded by corporate sponsors who dictate how the characters must act. This recommendation is based solely on the first 4 episodes of Majestic Prince, so it's possible that by series' end the rec wont fit as well. That being said, it's a rare enough occurance in anime that I wanted to call it out.
22-year-old Ryouta is an unemployed good-for-nothing who spends his days living at home and playing Btooom, a wildly popular online game that's sold over three million copies worldwide. Alongside other teammates, Ryouta battles it out with others using powerful bombs and sonar that can reveal hidden enemies, and his dedication has earned him the title of Japan's top player. But soon, Ryouta's pastime becomes a terrifying reality, as he and many others are dropped onto a tropical island and forced to play Btooom – but this time for real. Now, he and the rest must fight to the death by whatever means necessary, as the only way to win this deadly game is by killing seven of the other players.
Takuto’s relationship with his girlfriend Maki is on the rocks; she’s devoted to her research and keeps things bottled up inside, leaving their relationship uncertain. Life takes a tragic turn, however, when Takuto visits the source of Maki’s research: a giant metal being named Frank. While running an experiment to awaken Frank, the building collapses – and Takuto is the only survivor. Months later, Takuto awakens in a hospital with vengeance in his heart; and when the mysterious Dr. X offers him a new identity that he can use to bring down Frank, he accepts. With his new name of Ryu Soma and his new position in Funeral, a military organization charged with destroying alien invaders, Takuto sets forth to exact his revenge...
In the world of BBK/BRNK, It’s been ten years since Azuma Kazuki has been in Japan, and upon his arrival he is taken prisoner by a group of armed men. Azuma is saved by his childhood friend, Kogane Asabuki, thanks to a living weapon she wields on her right hand, known as a Bubuki. Learning about these weapons, Azuma becomes a Bubuki wielder himself and sets out on a journey.
Three men and two women have amnesia, and are selected to meet up and join together as a group. They are all ESPers with different powers that sublement each other, and are given a mission to save the human race. Once completed they will get their memories back.
The tragic story of Char Aznable, the ace pilot known as the Red Comet, and his sister Sayla Mass unfolds against the backdrop of the events leading to the One Year War. The Zabi family's rise to power, the birth of the Principality of Zeon, the early days of famous aces such as Ramba Ral and the Black Tri-Stars, the development of the revolutionary new weapon known as the mobile suit, and the road to war against the Earth Federation are all depicted onscreen for the first time.