Super Street Fighter 4, at the time of writing, is the most fun I've had with a fighting game, and arguably the most fun I've had with a single game in a long time. I mean a loooonngg time. Simply put, it is just a joy to play.
I think that one of the things that makes SSF4 so great is its uniqueness. The developers were not bound to the conventions and restrictions of reality. The fighters can all do crazy moves and are spectacularly agile by realistic standards. The special moves are absolutely ridiculous... fireball projectiles fired from the hands, flying punches and kicks, absurd throws and slams.
Focus attacks, EX special moves, focus attack dash cancels, and EX special cancels are some of the more advanced moves that players can use, although the game is still fun if you can't use them well.... they just allow the player to have an extra competitive edge if used correctly!!
Focus attacks are a charged attack that release automatically after about a second, or can be released at will. What makes them so important is that they can absorb exactly one attack. Two hits will break the absorption, as will EX special attacks. To absorb an attack and then release the charged attack promptly is key for getting some good surprise-attack counters. Also, victims of charged focus attacks flinch greatly and fall to the ground, likely leaving them open for another hit or combo.
EX special moves are basically jacked-up versions of regular special moves. Also, they all hit at least two-in-one, meaning they instantly break focus attacks and do extra damage. Also, most of them instantly do multiple-hit combos, and are likely to take priority over more powerful attacks. EX special moves are good for mixing up your gameplay and keeping the opponent guessing. The check-and-balance for this means that using one EX special move eats up a quarter of your "Super" bar, which when it's filled allows you do unleash a crazy attack... more on those later.
Stemming from the focus attack is the focus attack dash cancel (FADC). This is executed simply by doing a dash (double tap of a direction), and the fighter instantly dashes in the direction indicated, out of the focus attack. Simple in execution, but it is good for baiting opponents into doing special moves. Many special moves instantly break focus attacks, and many people will go for this focus break, and this is where the risk/reward of going for the FADC, or a "focus-feint" as I've called it comes into practice.
EX cancels are for players with exceptional timing and planning. Personally, I've only used a few but they are very effective when used correctly. An EX cancel consumes a quarter of the "Super" bar just like an EX special attack, and it immediately resets a fighter to neutral standing after executing a special move, assuming they are still on the ground. For example, many special moves can be canceled right after they make first contact. This allows a fighter to immediately execute a devastating combo of their choice while their opponent is completely open and vulnerable.
Super combo and ultra combo attacks are a different animal entirely. Also, they can be your enemy as much as they are your friend, because it's easy to be tempted to try them. Because they do massive damage, as soon as the ultra combo bar fills up (from taking damage), a strong temptation exists to go for the ultra combo and even the score. However, most of the leave a fighter very vulnerable for at least a second or two.
Super combos I believe are the less functional of the two, simply because it eats up an entire "Super" bar. The cost of going for a Super combo is not only being left open for a brief time, but also that the potential for EX special moves immediately resets to zero. Also, the ultra bar fills up every time your fighter hits about half-health, while the super bar fills up with every attack as well as every hit and block, it usually takes more than one round to fill entirely.
The fighting mechanics in SSF4 are great. They function such that the move sets are rather easy to learn, and therefore there is much more emphasis placed on wit and skill instead of memorization of combos and exploitation of nuances. Don't get me wrong, the two aforementioned features are present, but are minimized.
SSF4 has an incredible roster of fighters, and amazingly they all feel unique (except for ryu/ken/akuma, who basically only differentiate from each other with subtle timing issues and a handful of regular, non-special attacks). Many fighting styles are represented, although exaggerated. Some of the characters even use over-the-top, crazy move sets that don't emulate any specific martial art. Also, the fighters all have very distinct personalities, which are evident even from the subtle movement of their characters. El Fuerte is frantic and fast, Abel is calm and controlled, Balrog is a brute, Vega is vain, Ryu is confident, and all the other characters portray their attitude with everything from their neutral stance to their ultra combos.
SSF4 is a great fighting game, and I highly recommend that everybody try it. It's easy to pick up and hard to put down!!
Super Street Figther 4 gets a B lettergrade!!