I find it really solid ! A handful of playable charaters, different ennemies, easy controls except when it comes to ultimate I never managed to do one..
One problem that keeps me from playing it, though, is voice saturation..seriously, I understand, you want to give a retro feel to it, but I think you put way too much saturations on every voice clip, to the point it's practically unpleasant to play long at it..everything else is cool, so reducing voice saturation would be my prime suggestion about your game.
I'm currently in the midst of an updated build (can't guarantee when I'll get it done though) and I'm planning on making the voices high-quality and normal, alongside updated sounds as part of the many other fixes, upgrades, etc.
To do an ultimate move, just do the dragon punch input with the "unique button" (button used for shooting guns/throwing shurikens, etc.)