You are asking for different things. ISO files are usually images of CDs and DVDs and are larger regarding their size. NES, GBA and SMC files are "packages" of games that are emulated using a compatible emulator. For example NES type is used by SNES console, GBA by Game Boy Advanced handheld console. The emulators that have been released only recognize NES, GBA and SMC files. There is no way you could load an ISO file to these emulators.
And on the side note, the usage of emulators and games is strictly forbidden because you need to physically own the cartridges to be able to play the games.