So in a span of 2.5 years from the release of the first game to the release of the second it lost around 230k sales.... and you're surprised that the 3rd game isn't doing well now 18 years after Shenmue II was released?
Dude, releasing a game at that time for the Dreamcast was akin to come out with a Wii U exclusive during the 2017 holiday season when the console was pretty much dead and replaced already. At that point reaching 150k is actually a big achievement, because everybody has already moved on with the console.
The Nintendo eShop rating Thread: http://gamrconnect.vgchartz.com/thread.php?id=237454
The Steam/GOG key gifting thread: https://gamrconnect.vgchartz.com/thread/242024/the-steamgog-key-gifting-thread/1/