I don't see any ethical problem with emulators since their job is just to
emulate. But that depends on what kind of emulator we are talking about.
Example, the PSX emulator may be Free Software, but because they need a
proprietary bios I'm pretty sure that this make them unethical to use.
Now there is the second problem, and I think that this is what you are
talking about. It is the games problem. all commercial games released for the
console that you are trying to emulate (if nothing as changed since the time
they have been released) are proprietary, and for this reason it is unethical
to use them. But it exists a lot of homebrew that are GPL (and other free
software license) licensed (but I have to agree that if this is the only way
then there is no really need to have the emulator at all).
Then we have another important question, and that question is the
intellectual proprietary (damn I hate this term..) imposed by the company
that created the game, and the copyright associated to it. Some games are now
in the public domain (since a big time is passed), and because of this you
can (if I'm not wrong), take the game and play it (and even change the code
if you find a way to reverse engineer the game in question).
Now I can be wrong in some points, but this is what I know from some
researches over the years.
Hope it helps.
