If we're gonna get guests in future games (not sure it's an "if" however), then I see no reason it couldn't be one (or more) that we already got.

My first choice would be both the Alien and the Predator since I like them equally, but mostly if we don't get Baraka as DLC for MKX (I've already explained why in the third poll thread). In the Predator's case, I also just want it to get all of it's designs from the movies so we can see every Predators fight one another. If we get those plus Baraka as DLC for MKX though, then I'm fine with the Predator and the Alien not returning.

Second would be Freddy, so he can get the two things he sorely lacked in MK9: Dialogue, and Robert Englund's likeness (and only one glove). The Freddy vs Jason angle doesn't matter to me as much as it used to, though, so I don't feel he needs to return in MKX in particular. Whether he appears in MKX, a future MK game or a horror-themed fighting game, I just want him to get what he lacked in MK9.

Third would be Leatherface, though there's not much that needs improving. They got him right for the most part, and we even got to see him take on Jason, the Alien and the Predator. All he lacked was alts (these three designs should not have been variant-exclusive) and an outro where he makes a mask out of his opponent's face.

Fourth, Jason. Like Leatherface though, there's little that needs improving aside from the lack of alts.

The only one that needs that stay the fuck out of any future games imo is Kratos. Unless Sony can cool it with the special treatment.