The game has been taken as far as it can go, making it the seemingly definitive version to own if it suits you.
Super Street Fighter IV Arcade Edition sounds like a mouthful, but it really is only a slight extension of the previous installment. Included in round three of the Street Fighter IV hibernaculum are four new characters: Street Fighter III brothers Yun and Yang, Evil Ryu and Oni. Yun and Yang are every bit as dangerous as they were in Street Fighter III and made even so with their own SFIV-specific EX moves and tweaks. Evil Ryu is a deadlier version of our favorite solitary fighter with new EX Hyper Combos, faster strikes, a grotesque appearance----even some of Akuma's moves in his repertoire. And Oni is a radified Akuma who is roughly three times stronger than his original counterpart and has a couple of new tricks of his own. Interesting character additions to be sure, but they aren't likely to arouse an immediate interest among veterans of the previous release. Disappointingly, the updates for the Arcade Edition are relatively minor when compared to the original SSFIV----as there aren't any new arenas, new gameplay modes, new easter eggs, unlockables; nothing of the sort.
However, to its credit, the game emphasizes slight changes to character balancing and some new EX moves for existing fighters, and revisions have also been made to the online replay channels (a feature introduced in Super Street Fighter IV); including the ability to watch higher-tiered matches if the player earns a specific number of online points, giving them a greater incentive to brush up on their skills and learn strategies from potential opponents. These updates were more or less intended for online and local multiplayer competitions against human opponents as a way to keep things fresh, but theoretically speaking, it seems as if Street Fighter IV has gone as far as it can go. With SSFIV Arcade Edition being billed as the final game in the franchise, this would make it the defacto port to own if you don't have it already. And if by chance you DO have the regular Super Street Fighter IV lying around and want to upgrade, you can alternately download the Arcade Edition as an expansion DLC for roughly half the price of the packaged product.
I can only give my strongest recommendation of Super Street Fighter IV Arcade Edition to folks who have yet to own either the original Street Fighter IV or Super Street Fighter IV; as the Arcade Edition has everything they need to enjoy the fullest Street Fighter IV experience possible. Interestingly enough, it has even gone to great lengths to ensure that the original Super Street Fighter IV is not compromised in the least, giving purists the option to switch to that version instead if they so choose. Whatever your preference, Street Fighter IV has gone on to become one of the greatest fighting games ever to hit the scene in recent memory, invigorating a renewed interest in an aging genre. And Super Street Fighter IV: Arcade Edition seemingly accomplishes everything that it set out to do with the Street Fighter IV franchise, making it an obvious choice for anybody who has yet to play the game for the first time.