Although the illustration gallery found in Street Fighter Zero 2 has been removed, several new features have been added in SF Zero 2 Dash.
The first new feature is "Gouki Mode", which allows you to directly challenge the super-cheap Shin Gouki/Akuma in a fight to the finish on the plains of the hidden stage in Australia. If you manage to defeat this fearsome creature, you will sadly only recieve the game's credits.
The second addition to the game is the addition of new moves for several of the characters, including Sakura, Dhalsim, Sagat, and Guy. In addition to this, Capcom has also upped the number of alternate characters, and made them easier to access, with new "Championship Edition" versions of Ryu, Ken, Sagat, Chun-Li, and Vega/M. Bison, to go alongside Dhalsim and Zangief. Sakura also has a code which enables her to have pastel-colored outfits, and Evil Ryu and Shin Gouki/Akuma are now easier to access than in the last version. To add even more, Capcom put in a new option which allows for Super Moves to be executed at any time, despite what the Super Bar's status reads. (Thankfully, this IS just an option...
The last new addition and also the most surprising is the "new" hidden playable character: Cammy! Clad in her uniform and possessing all of her moves from X-Men Vs. Street Fighter, Cammy is a force to be reckoned with...in the Versus and Training modes, that is. Unfortunately, Cammy is not selectable in the 1P, Survival, and Gouki modes. (However, there is a Pro Action Replay code available which lets Cammy become available in the 1P and Survival modes...)
Don't forget that Guy has the Raging Bushin move in SFZ2' and SFA2G. HCB HCB + P @ Level 3. He grabs his opponent... the screen flashes as he kicks his opponent's ass. Not as nice looking as the Raging Demon, but it's still something to behold.