Apologies to the writers (and delusional Volo), but JE's writing wasn't even close to BG2. Ditto for the voice acting.
Look, I liked Jade Empire. I liked it enough to play through it twice, which a lot of people here haven't done. I thought the art direction and animations were fantastic, and I thought the combat was fun, if a little unbalanced. I really enjoyed the main plot, especially the sections in the Lotus Academy and Dirge. In fact, thought the main story arc was written well. It's the party members I have a problem with.
The supporting cast just seemed incredibly weak. Spider is dead on -- it's rare that The Protagonist sets off on an epic quest with such a bland set of companions. How is it that in BG2 deciding which five NPCs you wanted to take with you was like pulling teeth, and in JE I had a hard time picking one groupie to stroll around Bio's beautiful world with me?
Even the romance interests were boring. Seriously, BG2 had three romances that were much more compelling than any of the ones in Jade. Yes, even Aerie.
(I have heard rumors that you can have an ahem, "mano-a-mano" relationship with Sky, Jade Empire's dashing rogue. I haven't personally tried this, so I can't comment on the quality of this alleged "romance.")
Dawn Star showed more personality in the credits than she did the entire game. Sagacious Zu? That was a character with potential, but the finished product completely underwhelmed me. I got the "dangerous loner with a mysterious past" when I was hoping for so much more. I did enjoy the little girl/two demons dynamic of the Wild Flower NPC. The Black Whirlwind was over-the-top comic relief, the Princess was shallow, and the rest were forgettable.
All that may sound harsh, but Jade is still one of my favorite games on the Xbox, and I'll be purchasing the sequel when it's done. Another reason to be glad I bought a 360.