Huh? Your link is to some guy's recommended system requirements for his SNES emulator. This does not prove that it requires a 2.5GHz dual-core processor to successfully emulate a SNES. Perhaps a better programmer could do it with lesser hardware? Or a larger team of developers could spend more time optimizing performance?
Also, "recommended" system specs usually don't mean that much, especially from smaller/independent developers who likely don't do much testing and probably just recommend whatever system they use.
The only thing we know for sure is that people have been continually finding ways to push technology beyond what we previously assumed was possible.