SNES emulation on the DS will NEVER be possible.
EVER.
havnt we done alot of research?
What he's trying to say is that perfect SNES emulation, where all games are playable at full speed, with sound and transparencies properly emulated (you wouldn't believe how many SNES games are unplayable without them), will never happen. While the SNES has a slow main CPU which is easy to emulate, the real difficulty lies in its graphics (and partly its sound) processor. At the same time as they're more powerful than the main CPU, they're also proprietary and not very well documented, which makes it hard to achieve efficient emulation. A lot of CPU time is also lost syncing I/O between the various components.
As for games that had special processors built into the actual cartridges (Starfox/Mario RPG/Mario Kart/some others); they'll never run at more than 5-10 fps as emulating the special processors on top of the regular SNES using what limited processing power the DS has will be way too much.
Genesis emulation... don' t get me started. It'll never run acceptably, the DS just doesn't have the processing power to emulate the 8 MHz MC68k.