Xenogears probably has the best RPG plot of all PSX games (and I'm an FFT fan!), and I would rank it in the top five of all RPGs period. As stated, the philosophical & religious references can be superficial at times, but the great thing about the game is that no matter how many with latter-day religion, it never denounces any of them. The downside is that with all this lush imagery which seems to build up a cultured background on things, many things don't get fleshed out that much in the game (check out the Perfect Works translation for timelines and such). Still, 'though Xenogears overreaches a bit, it really turns the mundane "bad guy to defeat" plot upside-down...no other gives such a mature approach to the dang idea. Given you can get the game for about $25-30 used nowadays, it should be an automatic purchase for any fan of the genre.

Still, it's not without its downsides. The story, despite being nuanced, is a little slow-moving until reaching a few towns after the starting point; I've seen many people, including fans, complain about this. Truly, the plot is the game's selling point, which is why people are polarized about the second disc. Due to budget cuts, it's almost entirely story-driven, meaning text describes the action instead of it being acted out. It ties things together, but given the fireworks at the end of Disc 1, pretty easy to see why one would be let down. S'pose the only other common complaint I hear is that mech combat is boring. I found it much more intuitive and interesting than, say, materia junctioning, but that type of fighting is just supposed to get the player from Point A to B in the story -- it's not meant to revolutionize the world.

Anyway, having written a guide for it, I really can't quit piling on the accolades. Great script & translation, all-around characters, world setting, antagonists... Even if you paid $100, y'wouldn't regret a penny.