The excellent Windows-based Spectrum emulator Spectaculator is available for the iPhone and iPad. It comes with 10 games but most of them aren't what I would consider big names.

However, if you've visited www.jailbreakme.com, you can browse to the Documents directory of the application and drop other games in, provided they're a standard format. Hey, wait a minute, I've jailbroken! Hence...

Oh yes.