Epic beyond words.
-The scope of the story is staggering. You'll go through villages, forests, deserts, submarines, cities in the sky, endless towers, prisons, spaceships, battleships, glowing caverns, ocean rigs, and a plethora of cityscapes.
-Gears (huge robots) come in a wide variety and are always a sight to behold, the game designers did a great job of conveying a sense of scale throughout the game. Sometimes they're almost scary to look at.
-A range of well developed characters that are worth caring about. I found Fei to be a likable protagonist because he is a very human character - both strong and weak at times. Many of the villains are memorable as well.
-Phenomenal music. I especially enjoyed the Dazil and Aveh themes.
-Excellent graphical style and freedom of movement. 3d games with this much detail were a rarity back in 1998.
-Gorgeous anime cutscenes.
-The battle system is more interactive and fun than most other RPGs and sometimes you'll end up losing a key battle because you didn't use the correct attack combinations. Make no mistake, Xenogears is sometimes a very challenging game.
Bad:
-Some religious overtones that some people might not be into eventhough I thought they added a lot of style to the game.
-Sometimes the story is difficult to keep up with since it jumps between various times and distances quite a bit. Better to play this game for long periods at a time rather than casually or you'll end up forgetting what's going on.
-Skipping through dialogue you don't want to read is basically impossible.
-If you're not ready for a game that can easily take up to 90 hours to beat, then Xenogears is not for you. I know this because I beat it twice and enjoyed it even more the second time. Anyone that has experienced this game through to the end is truly praiseworthy in my book.