Soul Calibur on Dreamcast is, in my opinion, the best port of a fighting game ever made. In terms of competitive value, it's not the best, but in terms of content and sheer quality of everything else, it's just phenomenal and has never been topped.
The Quest mode alone is just so huge and well put together it leaves everything else in the dust.
I also liked part 2 (fuck you all, Spawn was a cool character), but I felt it didn't live up to the first, and I never even played the others.