Kouji, Ryou, and Gawl travel back through time in order to stop a world-shifting catastrophe. One of them is a Generator, with the ability to change into a powerful mechanical form, but the evil scientists working against them have their own nasty arsenal. Together, they must try to fit in as exchange students at a boarding house while making a desperate attempt at saving the world.
Some years into the future, a strange, unexplainable natural disaster has broken off a piece of the Japanese mainland. Known as the Lost Ground, it is now inhabited by people with Alters -- machine-like extensions of their own will. In order to keep the peace on the Lost Ground, the HOLY organization uses its own Alter capabilists to police the region. In the midst of the chaos is a young man named Kazuma, whose life will soon change forever as he discovers his hidden abilities, and how to wield them.
Date Kyosuke is a young man with problems. After being stabbed by his beloved mother, he discovers he has a long lost sister -- Runa. She is the first of many relatives that he and others in the story find tied into the seeming chaos of their lives. Date embarks on a quest to find Runa, aided by his new ability to turn into a monster; all the while in pitched battle at almost every turn with agents of mysterious organizations.
In the future, a devastating event known as Second Impact destroyed Tokyo as we know it, giving rise to the current day Tokyo III, a city under siege by mysterious lifeforms known only as Angels. Mankind's only defense are Evangelions, man-made machines piloted by Rei, Shinji, and Asuka, all who are the tender age of fourteen. The fate of Japan and the entire world now lie with these children, though they might not have the power to save the most important thing of all: each other.
One is about super powers while the other is about mech battles, but the shows have a lot in common.
Both have a female character who is overly extroverted yet secretly a nice person, and one who seems to have no social skills and is prone to awkwardness. The male lead in Eva shares elements with the 3 males in Gawl... questioning why he's doing his actions yet always trying to live up to the expectations people place upon him.
Both shows feature a mysterious shadow organization that is always manipulating things. Much like Eva, the show starts off fairly light-hearted but around the midpoint it seems to go out of its way to depress you.