Street Fighter seemed to work alright, but the SNK games had some MAJOR lag problems. I was playing a friend who lived a half hour away from me in SVC chaos and there was serious lag.
Kof 2k2 games were NEVER running full speed, I played people in my city or about half an hour away and it was just shit.
I never got a chance to try neowave (I had given up by that point.)
I don't know what the situation was like in America. There used to be hella Kof 2k2 players here. I bet you could find someone that might play in your area, it would be a lot of fun!
edit- When SFII' and Fatal Fury Special come out on XBLA here I'm gonna be playing those online like a madman!