I mentioned Mamehub not that long ago for playing older games online. It was ok, but a little bit laggy.. Just tried another program called ggpo, which is supposed to be about as lag free as possible.
Now, one of the guys I play with lives in India (Old friend from my college days), and we tested KOF97. Normally, we have pings between us of 400-600, which translates into at least a half second to a full seconds input lag. That wasn't a problem here.. I'm 100% sure a no life pro gamer would find some amounts of unacceptable lag, but they play within some ridiculous standard where you have to nail a single frame out of 60 frames to nail a move.. For my purposes, play seemed smoother as anything. Damned near perfect.
So yeah, 1990's/early 2000's fighters is what I'm playing now.