Sorry, EmuCon does not load games with file association... YET!
You can use any emulator that support loading games thru parameters (command line). yes, bsnes works with EmuCon just fine.
See "ec-readme.txt" for all tested emulators.
--- update --- next build will have support to run games using associated applications. I tested here with all SuperNES and PC Engine emulators and they all loaded just fine. EmuCon reads the application exec command line from the Windows registry...