Also, you can play the [tornado fang]ing games on a emu. On DS, PSP and PC.
So, why bother?
We'll focus on DS, since it's the relevant one here.
DS Genesis emulators currently suck. They utterly butcher the original display ratio of a Genesis game because the DS screens are much smaller. Now, by all means it's too soon to say if this game will change the display or if the emulation will even be good. Now, all signs show that they're retooling the games to keep them as close to the original titles on the DS' resolution, but Sega's got a questionable track record with emulation.
At the same time, this could be used in the same way Sega Classic Collection on PSP was used to make Pico Drive, one of the best Genesis emulators on the PSP.
I'm not thrilled about this, more so since I have these titles on Pico Drive PSP, but not everyone may subscribe to pirating with the flavor of the month card or have a PSP modded to run Pico Drive, so this isn't a bad move at all, especially making them portable.