Surely SF has always been about one-on-one versus play. Nothing else matters. And it's online offerings take care of that. Ranked matches give you the chance to earn battle points - which you'll be obsessed with building up. There's even the option to play through the arcade mode with access open to online players, who can interrupt and jump in.
This is a strong contender for best fighting game of all time. It's not everyone's cup of tea - if you know nothing about fighters you should hold off for Tekken 6. This is hardcore.