I have a retro-bit Sega bluetooth controller and it took me a while to figure out how to pair and configure it correctly. I'm still having an issue with handoff from Emulation Station to Retroarch but it's playable.

Anyway, I pair the controller using home+X. Then configure the buttons as follows in emulationstation:

Controller == Emulation station
B = A
A = B
Y = X
X = Y
Z = LB (ensure this configures as Axis 2+ not 2-)
C = RB (ensure this configures as Axis5+ not 5-)
LB = L2
RB = R2
Start = Start
Select = Select
Home = hotkey

This configuration in emulationstation matches the normal buttons for StreetFighter2 on sega without any customizing the controller config in the emulator. To ensure Z and C configure as Axis 2+ and 5+ i have to hold them longer than usual or they detect as 2- and 5-. Sometimes have to redo C and Z multiple times to get it to detect as +.

edit: this button config works but the problem I have is that after emulationstation goes black to enter the emulator, nothing happens until I turn off the controller (by holding the home button) and then turning it back on (by holding the home button). Then the game will play fine.