New wiiware, mdk2 has been ported over. Not really a dreamcast exclusive, but one very good dc game. From the preview shots, I'm not too sure of the video quality.

I am a huge shmup fan, and have a nice election going on my Wii of exotic like musha that I never got around to owning. Although mixed feelings about a nintendo console, it would be a fun place to have lots of dc shmups ported over.