Mortal Kombat ftw.
I'm horribly biased since I essentially grew up with MK,but bear with me here. There is simply no other fighting game like MK. Boon and Tobias had the balls to do something unique and different,and that's what they stuck to ever since. MK just has that refreshing vibe to it that you just can't confuse with anything. And right now,it's pretty much the only non-Japanese fighting game on the market. Say what you want about the gameplay,but in terms of storyline,design and overall atmosphere the Mortal Kombat series beats the everloving fuck out of pretty much every Japanese fighting game out there (the only possible exception being the SNK games). Hell,in this aspect,the MK universe wipes the floor with many modern (J)RPGs,and that's saying something.
*awaits patiently for the "OLOLO U FUCKIN NOOB FGHTING GAMEZ DON'T NEED NO STROILYNES OMGLOLZ"*
As for Street Fighter,Capcom at this point has pretty much run the series into the ground. I (begrudgingly =P) admit that it's a beautiful and delicately balanced classic,but that's no excuse to release 20 different versions of the same fucking game. But then again,it is Capcom we're talking about here... -_-
Jam it back in, in the dark.