From what I understand with FF7...
CloudxAerith was the original intended pairing. But mid development, they decided to pull the Disc 1 stunt, cause they wanted to try something different for once, and do a gutsy move like "kill off the stereotype deus ex machina driven female lead!" for a number of reasons. With that done, they thus elevated Tifa's role to be somewhat greater than originally intended, naturally, to fill the gaps that were probably originally intended for Aerith (and naturally, rewrote factors to fit Tifa's character personally, like actual past connections with Cloud, so Tifa played the part effectively, rather than feeling completely forced and an utter replacement.)
The end result is that FF7 pushes both pairings, kind of. Disc 1 is definitely CloudxAerith-centric, the game even goes as far as to have Cait Sith say "You two are a perfect couple! Poor Tifa..." but then they kill off Aerith, and she doesn't get revived, so whoops, can't push that pairing! ANd since CloudxTifa could easily be built upon, they basically decided to go from there.
Its worth noting that Aerith is clearly intended to be the canon date. Not only does she have the highest initial "Love" score, she also wins all tie breaks (and Barret loses all tie breaks
), IIRC.
Basically, CloudxAerith felt like it was originally intended, but due to changes in developmental stages, they decided to hook Cloud with Tifa at the end by killing off Aerith so they don't have to explain why Cloud randomly dumps her for the girl with a bigger rack.
You know, talking about these changes in FF7's plot mid development made me realize just how much more insulting FF12's changes were. FF7 changed stuff and managed to make it work, cause they didn't do a half assed job, like make Tifa work WITH the scenes, not be forcefully shoved in there so she can get boned by Cloud by the end of the game.
FF12? "Hey, Vaan's the real main now in BASCH's story! No, beyond the early narrative, we haven't adjusted the plot at all to compensate for Vaan being the true lead...so we accidentally kind of main Ashe the game's protagonist...but then Balthier is the self proclaimed 'leading man' so all the fans are going to claim him of course, since he's just THAT DAMN SEXY!"
FF12, I like you, but dear god did you fuck up badly on plot in so many ways.