Xenosaga
parts:
1
2
3
It's got everything I look for in a Sci-Fi video game RPG.
A great story, good CG (computer graphics), excellent VAs (voice actors), and good game-mechanix.
The games are currently out of print but maybe available at your local gamestore and/or ebay.
The strategy guides are a must for these games and although you can play any one of them as a standalone game it is better to play all three for the maximum enjoyment of the story.
And Kosmos....