Welcome aboard, man! I guarantee that this will be the most fun you’ll ever have without going on a traveling or wilderness adventure, and/or taking your clothes off. Hope to see you on GGPO. With your clothes on.
As of right now, discounting people outside of the big cities who simply do not have access available, SF4 is the most played. Almost every SF player who can’t play it right now wishes they could. It’ll be interesting to see just how much the scenes for other, older games are affected by SF4, both short-term and in the long run.
Previous to this, 3S was definitely the most popular with both the casuals and hardcores. Its reign of dominance began definitively around the time that SFAC was released on PS2 and the Justin/Daigo video showed up on YouTube. Honourable mentions include MvC2 because its players are just so frickin’ hype about it, and ST because there will always, always be people who are still playing SF2.
I’ll make a special note of A3 too, as the fanboys’ favourite because it remains hugely popular with that certain demographic but not necessarily with hardcore SF players. All those dudes who love SF for its storyline, this is their game. There are definitely some legitimate, understand-competitive-play types out there who prefer A3, but for the most part the game is a scrub-magnet. Up until Guilty Gear and the proliferation of localizing actual anime series-licensed titles, this was the must-have fighting game for anime fans. At best, they enjoy themselves all playing Akuma and jumping around a lot. At worst, they wear costumes, complain that fireballs are cheap, and talk about how much better their own personal MUGEN arrangement is than the official game their playing. That, or they play world tour mode by themselves and think deeply about the character intros and endings. Sounds cool, hey?
(Hahah, how can you tell I’m biased? Huuuge overgeneralizations, I know, so nobody get their undies in a bunch, okay? :bgrin:)