If we're talking games with Street Fighter Characters, then probably TvC on the Wii (which is why I'm dying waiting for MvC3). For pure Street Fighter, I would say Alpha 3.
Yeah, SFA3 was the best IMO. I still play it til this day.
I grew up on the many versions of Street Fighter II, and Super Turbo being the best version I'll go with that.
Yet, I still love SF4 and Super: AE etc., because it got me back into playing FG's after more then a decade hiatus.
So far, I love Super Street Fighter IV Arcade Edition. Third Strike is better on the arcade machines anyways 'cause I have tried every port of it and none of them are as the arcade version as every fan said. I dunno, any Street Fighter game is good for me to execute the moves especially Pocket Fighter. SFxT is likely a party game to me.
I'd played all the Street Fighters in the arcade and cross over with SNK. Besides the Street Fighter II Champion ediion as you can play the bosses. Street Fighter III rd Strike is the best,have all the classic characters mixed with the new generation,plus the tap movement button and killer super move. But the worst cheap boss in the series,he regenerates health and it just sucks near winning him when his powers prevents you from coming close to him while a rain of metorite raining down. Need to keep close to the boss,but not getting a pile driver.