fast requires clever coding tuned to the underlying hardware.
Only Sony (or possibly a studio that had done a lot of professional PS2 and PS3 development) could write a workable software-only PS2 emulator for the PS3.
Which would be pointless, unfortunately. Whoever said this "buy a PS2 emulator" thing originally didn't know what they were talking about. To get a PS2 emulator to run on a PS3, it would need to be built for the Cell, not the Intel-type chips. The PS2's hardware was pretty unusual from what I understand, specialized and hard to emulate well. Getting it to run