Just for the sake of information, I can confirm that Mortal Kombat II does work off of the Retrode 2.
I have no information about Street Fighter 2. However, it is fortunately one of the ROMs that are sold by Sega on Steam, and for very cheap. There are instructions by various users for getting the ROM out of the Steam folder and using it on any emulator you like, such as Kega Fusion.