Ditto on the general Xenosaga trend: played 1 and enjoyed the characters and plot, but then 2 made me wish I hadn't spent the money on the game. My brother has played 3 and keeps telling me to give it a chance because it actually has a solid gameplay system, but the shadow of 2 just won't go away. =/
Xenogears... was a fantastic game, though I felt like it was really strongest in the earlier acts. Disc 2, where the team clearly ran out of budget... still some great plot there, but the gameplay took a hit.