With Apple's experience with running in emulation they could do an "iGame"
Emulate all the old consoles (add your favorite console here) and a mame port and sell the games on iTMS (iGS?) with their DRM at $5-10 a pop and have a winner.
I like your idea. Even before the Wii's Virtual Console (or the Xbox 360 Marketplace, to be fair), the sales of the Atari Flashback 1 and 2, not to mention those all-in-one emulation controllers by Jaxx's Games confirms that consumers would love the chance to play the old classics.
Just add support for stereo, upscaling, multiplayer, etc. and they would sell massively.
Even without the participation of Nintendo (for the NES titles), I'm sure Sega would be anxious to contribute titles, whether in the form of the original arcade ROMs, or from the various Sega platforms like the Master System, MegaDrive/Genesis, Saturn, Dreamcast, etc. You could get Atari's titles - including arcade - as well as titles from the 2600, 5200, 7800, Lynx/Jaguar, plus the computer platforms like the 400/800/XL/XE and the ST/STe/TT/Falcon.
Add to that, whoever owns the rights to Commodore's wares, plus the Intellivision and the ColecoVision....
This would truly rock...be low-cost, and highly profitable.