Here's my boring list, in order of character preference.
Soul Blade/Edge - Mitsurugi*, Li Long
Soul Calibur - Mitsurugi*, Astaroth, Ivy, Nightmare, Xianghua
Soul Calibur II - Mitsurugi*, Astaroth, Nightmare, Xianghua
Soul Calibur III - Setsuka*, Astaroth, Siegfried, Mitsurugi
Soulcalibur IV - Setsuka*, Siegfried, Astaroth, Mitsurugi
I'm boring.
I played enough of all of them where I could use just about anyone decently.