For 2d fighting on pc - you should try mugen!
It is a 2d fighting engine, with converted and redone characters from close to every 2d fighting game ever made - aswell as other odd pixel-based characters.. it's a bit hard to explain.. but picture a character select screen with 100+ slots, with everything from sf2/sfIII, snk games, ggx fighters (almost exact as the original characters from the games).. along side cloud/link/sora..
you find and download characters, and backgrounds that people has ripped or created, and create your very own battlefest..
I for instance have 8 versions of Ryu from every street fighter game, just to find out which version is the most kickass.. :P
aside from my ramblings - look it up if you're interested.
start here:
http://www.streetmugen.com/site-us.html
- and then there's always our beloved google
Mugen!