"Perfect" emulator? Given how complicated Cell is, I'd expect something like 1THz minimum needed to run it perfectly, less if you can get it working in parallel. Thing is, this isn't a perfect emulator. It cheats. It has to cheat in order to run like this. Emulators are going to have special code related to the most popular titles on that platform. Read up.
Now, take that 3.58MHz SNES CPU and multiply it by a thousand for the PS3's 3.2GHz Cell. Not only that, the PS3 can run in out-of-order execution and because Cell is Cell, add in SMT (think Hyperthreading) and seven additional coprocessors.
I'm not sure we'll ever see perfect PS3 or 360 emulation. Best we can hope for is to deconstruct the games and retool them for x86, or build emulators that cheat. Perfect emulation is simply not feasible. You can get a
game working by tweaking things until it works, but you can't get all
games working without a few orders of magnitude more computing power.