A lot of people refer to this game as the Evangelion of JRPG's. It's pretty amazing, for those of you who have never heard of the game..
Xenogears initially takes place on Ignas, the largest continent of the Xenogears world, and site of a centuries long war between the nations of Aveh and Kislev. A church-like organization known as the Ethos has excavated giant fighting robots called Gears in the name of preserving the world's culture. These Gears have had a major effect on the war and have almost entirely replaced the need for human infantry. Although Kislev originally had the upper hand in the war, a mysterious army known as Gebler appeared and started providing assistance to Aveh. With Gebler's help, the Aveh military not only recovered its losses, but began making its way into Kislev's territory.
It's a complex, very controversial story. What with trying to destroy God and what not.
The battle system is one of the games biggest highlights. You can also fight with the characters as they are without Gears. It's a little cool and clever combo system. You build up your attack level by doing regular attacks and not following them up with combos until at least level 1, 2, or 3 so you can pull off some flashy, damage dealing stuff. It also works this way for the Gears too but a bit more complicated and limited movement compared to being on flat ground.
and if you are dedicated enough or know how to use google you can use the latest pixel shaders to make the game look even more epic.