The dreamcast is a damn fine machine still with a very active homebrew community.
Regarding Shenmue - I agree that it's a game that divides the world. Graphically it's superb with audio to match but the game is just so damn slow...z.zzzzzzzzzz.
This is because the game is played in real time - I.E. if you arrange to meet someone at a set time then you have to wait until it's that time of day. While you can interact with every character, the non essential one's utter the same few phrases between them which becomes extremely irritating.
You even have to get a tedius job and then perform those duties.
Granted, the fight scenes are well done but it's one of those games that you will love or hate - there's no middle ground.
Sonic 1 & 2 are brilliant though. Chu Chu rocket is a brilliant puzzler. The dreamcast has the best version of Half-Life (you won't get that in the shops though!) and Midnight Street Racing has cars that handle superbly (this evolved into Project Gotham on Xbox) and one of my fave games on Dreamcast is 18 Wheeler. Floigen bros is worth a try as well and seeing Soul Calibur in action makes you wonder why the DC was canned.
I love my DC!