The App Store doesn't allow emulators unfortunately and bans any that they come across. However one app has done a sneaky job of hiding an emulator in plain site.
Remote File Manager is an iOS app that allows you to access files from your Dropbox or FTP servers. It allows you to the view content and open all types of files. But one thing that it doesn't tell you is that it has a hidden SNES emulator.
You simply need to find SNES roms with the SMC file type, a quick Google search and you'll find a ton. Put them into your Dropbox. Access Dropbox through Remote File Manager and open the rom. It'll load perfectly and works very smoothly.
Get it before it's taken down from the App Store!