Emulation is so popular now that you can safely say that every single gaming console will (eventually) have an emulator created for it, or at least attempted. Cutting edge consoles like the 360 and ps3 will certainly lag behind in development because:
a) these are brand new, typically undocumented-to-the-public machines that are being emulated
b) heavy amounts of security layers have to be broken through
c) the consoles run so fast that you would need an incredibly powerful PC in order to emulate them at speed. (I believe the rule of thumb is that the emulator has to be running at a minimum of 5x the CPU speed of the system being emulated)
Emulation is about preserving outdated consoles for history/nostalgia. If you are trying to play current generation consoles, you will be disappointed.
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I think it is safe to say that every or virtually every SNES game is playable via emulation now. It's not so much that the games themselves had to be cracked, but the emulators themselves had to emulate whatever tiny tricks the game developers used to make sure the game was legit, so any lists of compatibility would be per emulator. Some emulators play certain games better than others, so you'll just have to explore.
-jeff!