If you're looking for manga similar to Beast Wars Neo: Chou Seimeitai Transformers, you might like these titles.
In the year 3195, there was a war between an army of robots and the humans. When Shaian, a sentient combat armor, lost his companion in battle, he shut down until his internal systems spotted a new human. It's now almost a 1000 years later, and Shaian's greatest enemy is still alive and doing battle in Brazil. With a new friend`s help, Shaian may be able to stop this evil force before another war rages over the continent.
Years ago, after watching his family die at the hands of the Vegan empire, Duke Fleed managed to escape, stealing the powerful UFO Grendizer that the enemy used to destroy his planet in the process. Eventually ending up on Earth, the boy was adopted by Dr. Umon and given the name Daisuke, intent on living out the rest of his life in peace. However, when his father and the mecha pilot Kouji Kabuto realize that the Vegan empire has arrived at Earth to repeat history, Daisuke is forced back into the pilot's seat to save his new home. Alongside Kouji's flying saucer, can Daisuke and his Grendizer stop the fleet and save the world?