Yeah MK Gold added Baraka, Mileena, Kitana (who was only accessible in some home versions of MK4 with a gameshark I believe, but here he's a normal character), Kung Lao, Cyrax and Sector (secret character). However it ALSO has the new characters that were in the home versions of MK4 (but not arcade) like Noob Saibot, Goro (he's playable too IIRC, with a cheat, and he normally functions as a sub-boss, very tough!), and "Meat" which really isn't a new character, just a bloody muscled skeleton that has the moves of whatever character you chose normally. The new characters get new weapons, and you can do a free weapon select so you get any weapon you want, so another character can use Cyrax's lightsaber.
Also the endings in MK Gold are super high res versions of the CGI rendered endings which were (I believe) introduced in the PSX version, and you get new endings for the new characters.
MK Gold, as I've heard was originally very buggy when it came out, and so Sega issued a product recall on it. The original version was on a gold colored disc, but the 1.1 updated version was a red disc. I bought mine used for like $10 from a Hastings store and Marvel Vs. Capcom as well. It's not really as bad as people say, though I admit the "3-D" graphics took some getting used to (then again the gameplay is almost exactly the same as MK3, minus all the insane combos, you have "max damage" that stops you from getting too many hits). There is very little 3d movement (basically just sidesteps) and the weapons are just hack and slash deals you can whip out if you're quick, or toss a rock or something at them.
As far as Xbox emulators, are you sure? I knew a lot of preliminary emus had come out but thought they were all incomplete or only played demos or something.
IF there is an emulator that will let me take a purchased Xbox game and pop it into my DVD-ROM drive and play it on my PC, I'd definately go for it, all I'd need to do is buy the games. I never owned a PSX, but I bought PSX games I wanted when the emulation was perfect, so I could just play them straight from the commercial cd in my drive (and with better graphics than the original and less load time!).
Can anyone provide anymore information? I would be surprised if it were that easy. But maybe I've been away too long...
PS: If we're not allowed to discuss that sort of thing here, then fine, I understand, please PM me about it.
I wouldn't pirate these games, but if I have to burn a copy or something to make it playable on a PC that's cool, if I own the original.