Allthough I beleive Shenmue to be the greatest game of all time, I wouldnt say that Shenmue II is better than the first one, as it gets a bit strange towards the end, (I wont spoil it for you!) but its still a fantastic game, a worthy addition to your DC collection, and will leave you wanting more!
but the DC version is Japanese/English subtitled.
Games you must own are:
Jet Set Radio
Shenmue & 2
Metropolis Street Racer
House of the Dead 2 (Using the light gun)
Daytona USA 2001
Space Channel 5
Virtua Fighter 3tb
Phantasy star online
...where do I end
oh, and a few strange games worth a try:
Seaman (Strange virtual pet game which you can talk to using sipplied mic, very strange how well it actually works, and strangely addictive, US released only but it works with a boot disc on a PAL DC)
Sega Bass fishing (if you drink alcohol a lot (like me), using this game with the official Dreamcast fishing rod, with a few drunken mates is a great laugh)
Occasionally you will find most of these games available on EBay brand new, still sealed, so go and get em while you still can.
Oh, and Dastardly, you can now add the wonderfull Dreamcast to your Biography, lol