Mother mercy of God I now have Street Fighter IV. Within a single hour of remembering Shoryukens and Hurricane Kicks you will have figured out Ultra and Super Combos and only be beginning to realize how EX moves happen to fit into the overall strategy of the game.
The most outstanding fighting game I have ever played, with the possible exception of Dragonball Z: Budokai 3 (and if you haven't played Budokai 3 then just shut the fuck up until you have and stop judging now). Mostly because its simple execution and open concept hide a much, much more complex fighting game where everything is important - where you actually care about distance from your opponent, reaction time, gauge levels, and whether to use Light, Medium or Heavy. In gameplay Budokai 3 and Street Fighter IV are nothing alike, yet both are simple systems with fairly light learning curves which end up hiding incredible strategic fighting experiences.