Soul Calibur all the way. Mortal Kombat has a few too many cheap tricks for my taste (or at least Armageddon did), I don't like how most people in Tekken are just punch/kick people without weapons and I haven't really played much else besides that. I tried Virtua Fighter and freaking hated it, but that's about it.
That said, Soul Calibur 4 can go fuck itself with a claw hammer. I wish they had stopped at 3 rather than release that monstrosity. 3 had everything. 2 different campaign modes (both of which were fun and had a good story), a fantastic arcade mode, a character-creation system that WASN'T just re-skinning existing characters (plus if you really wanted to re-skin characters with the creation system you could, it's just that they had their own styles too), a lot more characters, and there was no micromanagement of equipment going on. You picked what weapon you liked and that was that. The clothes and other crap did nothing and was just for show. Like TF2 hats. Then SC4 comes and says "Fuck all that! Who cares about having a good game when they can have Darth Vader or Yoda!?"
I care, SC4. I care. I don't want campaign modes that are 3 seconds long with literally zero story. I don't want arcade mode to be the same damn thing, or the optional fight-till-you-drop mode. Yoda is broken and Vader sucks, and neither of them belong in the pretty cool universe you created. If SC5 ever comes, I want a return to what 3 gave us, and I hope that fans of the series do, too.
For the TLDR crowd: Soul Calibur 3 was a fantastic game by just about any standard and Soul Calibur 4 will most likely be in the hospital with a torn sphincter due to claw-hammer-fucking.