Didn't Steve jobs say Mac OS X was "Processor Independent" doesn't that mean that it can be installed on any processor in lieu of windows?
There's more than CPU support to running an OS. All of your hardware, including hard drives and the keyboard, has to have proper driver support.
Doesn't that also mean that emulators should try to emulate the OS instead of the Processor?
You're thinking about this backwards. You emulate hardware to allow the OS to run. You don't emulate the OS to match the hardware you've got.
Additionally, despite OS X's processor independence, the shipping packages are built specifically for the PowerPC platform and not for the Intel platform. The Intel code is a separate codebase all-together, I'm sure.
It's like Linux/UNIX/BSD, if you think about it. Those OSes, for the most part, are processor independent (hell, look at NetBSD!). That doesn't mean that the PPC build will run on x86, though, nor is the inverse true. You have to have specific builds (or "fat" builds that support multiple CPUs) for whatever CPU your system is running.
Here's hoping I answered more questions than I created.