maybe i'll send you a private message, since i have ranted about the "why" for over a year now, and i made a promise to myself and the mk9 fans on here that i wouldn't go into a rage hate over why i don't like mk9.
anyway, as far as street fighter hd remix goes, street fighter has always existed in the realm of animation. so even though 3d animation and 2d animation are different, they're similar enough that moving from one to the other wasn't a jarring or confusing experience. so even though ssf4 and sf2 and all the other sf games are different, you can draw visual links between each game, despite the new look of sf4. for example, ryu looks the same in each game; he moves nearly the same way he did 20 years ago, and only some of his moves have been slightly enhanced.
yes, mk is all about change, but the one thing that always kept the games tied (in spite of costume changes, and run buttons, and dial combos and the removal of fan favorites) together was the digitized look. for me, it would just be a strange juxtaposition to see a digitized mkhd exist alongside mk9, because, if mkhd is even possible, then ultimately you would have to ask the question that i've asked on here before: "what purpose does 3d modeled mk even serve, if mk is back in 2d?" 3d modeled mk made perfect sense when the game was in a 3d environment, but if mkhd can be made well, then why does the mk franchise still need 3d models? so you see, imo, digitized 2d mk and 3d modeled 2d mk kinda cancel each other out. it would make more sense to have two stylistically different games if you had--for example, full 3d mortal kombat with 3d models, and 2d mortal kombat digitized. each game would serve a different function, so i could forgive the visual difference more.
clearly, capcom needs to use 3d models, because i can't even imagine the amount of time it would take to animate sf4 the same way or better than they animated sf3 third strike, and making tweaks to a hand drawn animated game, with a cast of nearly 40 characters, would be insane. this would not be the case for a new 2d digitized mortal kombat game. in order to make adjustments to the game, all you would need is a camera and the actors. the only downside to digitized mortal kombat would be having to deal with an actor's death, an actor's ego, and no elaborate cut-scenes. barring those three things, it really makes no sense for a 2d mortal kombat game to use 3d models.
if mortal kombat hd existed alongside mortal kombat 9, it would be the visual equivalent of street fighter the movie game existing alongside those 2d animated street fighter games, and in that instance, it was just weird.