The Electronic Frontier Foundation watchdog group has posted it's top ten most wanted for patents that could upset the public domain and nintendo made number eight. http://www.eff.org/patent/wanted/patent.php?p=nintendo
Not too surpising though Nintendo has been known for shady business practices (like making developers sign contarcts to only develope for their consoles etc.)
Uh... they already did. Nintendo patented the concept of emulating Gameboy Advance. http://www.theregister.co.uk/2004/03/12/nintendo_patents_handheld_emulation_software/
They didn't patent "general" emulation though, but emulation on low-power platforms with game-specific optimizations. So far they've used the patent against PDA Gameboy emulators.
And as before, it won't hold. HOw many GBA emulators are out there? If they could do this (and it was binding) Microsoft would've pattended web browsers, word processors, spreadsheets, and anything else useful. 3 sheckles says we have good GBA emulation on the DS/PSP one year after they're cracked.