If you liked the Planzet anime, the Anime-Planet community thinks you'd like:
It is Universal Century 0093. Char Aznable believes humanity is being held down by Earth’s gravity and seeks to end their suffering. With the help of his Neo-Zeon forces, he seeks to drop the asteroid Axis down, leaving the Earth uninhabitable by creating an apocalyptic winter; doing so will force humanity into space, the only way to truly evolve. The only one standing in his way is his rival Amuro Ray and his Londo Bell forces. Amuro must use the full power of his Nu Gundam in order to have a chance in stopping Char. History is in the making as the two rivals battle it out one last time.
So, you like anime movies about mecha where they have to stop stuff from colliding with the world? While Char's Counterattack requires more then a little context - it is a conclusion to an arc that includes the first two or three Gundam series - it basically provides a more satisfying example of this sort of mecha story, one I can only suspect that Planzet may have been 'inspired' by.
In the future, a devastating event known as Second Impact has destroyed Tokyo as we know it, giving rise to Tokyo III - a city under siege by mysterious lifeforms known only as Angels. Mankind's only line of defense are the Evangelions, a set man-made machines piloted by a trio of fourteen year-old teenagers, Rei, Shinji, and Asuka. The fate of Japan and the entire world now lie with these three children, though they might not have the power to save the most important thing of all: each other.
Disturbed by Japan’s emergence as the de facto world leader in robotics, the United Nations instituted an international treaty requiring stringent regulations. When vocal objections failed to overturn the decision, Japan chose to withdraw from the UN and vanished from world view in a self-imposed isolation made possible by an impenetrable electromagnetic barrier. Now, ten years later in 2067, the only means of contact between Japan and the world belongs to Daiwa Heavy Industries, a powerful corporation monopolizing the world’s robotics market. The uneasy truce comes under question when SWORD, a U.S. special forces unit, finds disturbing evidence that Japan may have sinister designs for the rest of the world. SWORD must now infiltrate Japan to separate fact from fiction, but is anyone prepared for the truth?
Plot? Who needs plot when you've got CGI?
Vexille and Planzet provide fully CGI anime, although their plots are nothing more then a mishmash of science fiction action cliches - in Planzet's case, very obviously the plot of a Gundam movie (and a pastiche of mecha in general), while Vexille's influences are cyberpunk and the Matrix. Pretty much you get CGI sci-fi action that's empty and forgettable, but if you watched one for that, the other also provides.
Nagamine is a young high school student who lives a fairly typical teenage life: hanging out with friends, attending class, and falling in love with a wonderful boy. But when she enlists in the galactic army, who is desperate for candidates to fight an alien war, she finds herself drifting farther away from her first love, Noboru. In the depths of space, where a simple email takes eight years to be delivered, will their love truly flourish, or simply fade away?
Hoshi no Koe is more of a romance, but is miles above Planzet in every way. The animation is stunning, the plot is similar - people must sacrifice themselves in a way to pilot mecha to take down invaders - and overall it's just better. A different tone for sure, but try it out.