I completed Shenmue I and began straight away Shenmue II as if the two episodes were part of the same game. And what an odd feeling, I now understand why some fans complain so much about the difference of atmosphere.
About Shenmue 1, my vision is still the same. It's more an experience than a true video game until the excellent last hours with the story gradation (apart the Chai fight which lacked of epicness after the Mad Angels chapter). It is probably hard to enjoy the full game if you're a newcomer or someone who did not know the early 00's era.
That's why we should recommend to all newcomers to do the two games in a row and insist strongly on that point. Shenmue I has no sense without Shenmue II from a modern point of view.
Oh, and I got the famous Nulldc issue with Nozomi bike cinematic without music.