Actually, for Shenmue 2, I actually liked the english voices better around, this time. The original Japanese voices for Shenmue II were quite uninspired and, for the most part, lacked any emotion to them. The english voice acting was much more colorful, and enjoyable. Wel, except for 1 single line of dialogue spoken by Xiuying, but outside of that. I also like the way the english versions spoke the chinese names a bit closer to the original chinese pronunciations. Japanese stuck with the romanji, the whole way through, and of course butchers the names in the familiar japanese way.
The first Shenmue, I did like the Japanese voices better, but the 2nd one seemed clearly to take Ryo out of Japan and into China. A location that tends to support english better than japanese. Also it's more believable that in order for Ryo and the inhabitants to communicate, they use a median language like english. It just seems that the "real original" language changed between the first and the second one. Still, my opinion was that the effort wasn't there in the Japanese voice acting for most people in it. The english ones at least sound like they tried harder and quite a few voices are quite amusing and fun to hear. Much better done than Shenmue 1, this time with actual emotion behind their voices.
I don't know about whether the lack of sales of Shenmue II had much to do with the Xbox or the idea that the amount of Dreamcast fans on the Xbox weren't enough to make a huge seller. Heck, the amount of Dreamcast fans, at the time, on the Dreamcast weren't enough to make that version a decent seller. If it was on the Cube or the PS2, I doubt it would make a hint of difference as we've seen Sega titles flop on both systems.
