Heart of the DragonStar
It's just fun.
Although, I liked III better, and III wasn't much of a bump up from II. II being mostly a graphical update from I. So, I guess I can see that.
I dunno. Granted, I don't have Soul Blade or Soul Calibur, but I find Soul Calibur II to be a masterpiece of fighting games, if not gaming in itself. I found SCIII to be fine. Not as great as II, but a good direction. However, even though I count SCII as my fav, it was SCIV that got me back into the series.