@Zing I have tested it seems to be woriking. I have mixed, GB, GBA, SNES and MD roms, and I can play with all of them except the megadrive rom.
As extension of this system I have configured with the "zip" extension. The problem is defining the cores and priorities. It works better, when I include all cores from all systems with the same priority 1, but it is not working with Megadrive (obviously, the rom works in the megadrive folder). I think it is not the best option, but I feel close to an optimal solution.
Now, it is my new system. In platform I have snes, but I dont know waht I can write. Do you hace any suggestion? I am searching information about the cores and priorities, but I didnt fing any explanation yet.
<system>
<fullname>StreetFighter</fullname>
<name>sf</name>
<path>/recalbox/share/roms/sf</path>
<extension>.zip</extension>
<command>python /usr/lib/python2.7/site-packages/configgen/emulatorlauncher.pyc %CONTROLLERSCONFIG% -system %SYSTEM% -rom %ROM% -emulator %EMULATOR% -core %CORE% -ratio %RATIO% %NETPLAY%</command>
<platform>snes</platform>
<theme>sf</theme>
<emulators>
<emulator name="pisnes">
<cores>
</cores>
</emulator>
<emulator name="libretro">
<cores>
<core priority="1">snes9x2005</core>
<core priority="1">snes9x2010</core>
<core priority="1">snes9x</core>
<core priority="1">snes9x2002</core>
<core priority="1">mesen_s</core>
<core priority="1">mgba</core>
<core priority="1">gambatte</core>
<core priority="1">mesen_s</core>
<core priority="1">tgbdual</core>
<core priority="1">sameboy</core>
<core priority="1">gpsp</core>
<core priority="1">mgba</core>
<core priority="1">meteor</core>
<core priority="1">genesisplusgx</core>
<core priority="1">picodrive</core>
</cores>
</emulator>
</emulators>
</system>