All fair points, Kuro, but as consoles keep getting more and more like PC's onto themselves, emulating them will only get easier, not harder. Assuming the companies that make the consoles don't release them for PC in some way shape or form themselves, which, then, precludes the need to actually emulate it at all... Or to buy it, for that matter, if you have a kickass PC.
The older hardware is harder to emulate, because it often used exotic components that have particular quirks about them, and the language used is weird, etc... Any number of reasons. Newer hardware got easier, and easier, and easier. But there are still problems.
Now, we could bruteforce the problems away in some cases with the older consoles. We had the power. Processors/GPU's that are thousands, millions, billion times faster than what they used. We could just say "fuck it" and bruteforce away. This becomes a problem with newer consoles. They're often easier to emulate in some cases, but in the cases they're not, we can't just simply bruteforce them. Newer hardware being four, eight, or even sixteen times as powerful is not enough. We'd need much more powerful hardware to simply bruteforce *those* problems away.
So we need a way to make better emulators, which need a better understanding of how the hardware talks to software and how it all works, so we can make a translation to make it work with PC just as well, or at least close to as well, as it does on the native console.
So if a newer console has weird hardware, and a weird/modified OS... We need to figure out what is going on behind the scenes. But doing that is hard. Reverse engineering that shit is haaaaaaaard. But everything's hidden behind patents, under lock and key, away from sight and difficult to access by those who need the information the DEV's had when developing games for the console, and in some instances even more than that, they need to know shit only the engineers who designed the console had access to.
That takes time. A whole effort by a very large community can eventually reverse engineer stuff well enough that it can run basically everything, with 100% fidelity, as the SNES community has done for its console. I doubt the Saturn has a following as large as the SNES does...
And newer consoles? Well, they're DIRT CHEAP in many cases. Damn, i know people who'd gladly simply GIVE AWAY a N64 that's just taking space, or a PS1, or even a PS2/Xbox. Or maybe sell them for next to nothing. I know people who did this - though i only found out after the fact because i actually want an N64/PS2/Xbox.
So: Lack of a large community, difficulties in accessing the code, plus the fact they're still new, all contribute to newer consoles being the worse at being emulated.
But all this changes when consoles become almost exactly like PC's...
So we wait a few years, and all these consoles you mentioned have problems with emulating as of right now will be better emulated. A few more years, and the newer stuff too. And if the trend continues everything will be either available on PC, or be capable of emulating on a PC.
AT LEAST THAT'S WHAT I CHOSE TO BELIEVE! MY UTOPIA! DON'T TAKE AWAY MY DREAMS!