A good one-button fighting game? How can it be?! And yet it is. If you can find a copy of evil zone (good luck) grab it!
Now, as to depth, don't look for it here. Outside the involving fight engine, there's little replay value, two extra costumes per person, and 1 extra character. I can't explain it, but the game's ridiculously addictive without the encyclopedia of extras you get with a soul calibur.
The main issue is finding it. Most folks at the gamestore won't even know what you're talking about. If they do, only buy your games from that store from now on, because those employees are worth your patronage.