@Greg:
Do you know who she really is?
Yeah, and she still bores me to tears. I'll admit knowing who she really is makes her significantly more interesting, but had her identity been made more clear in the game itself I would've cared more. I, as did many I assume, figured it out after having beaten the game, so I really didn't care as much.
And to be honest I'd like to know where the hints were about the GFs having negative effects, because I honestly just can't remember there being any kind of suggestion that something was up.
And as far as 8's twist being something that could actually happen, well sure, but so is personality displacement. I think my issue is that it just wasn't handled well, all of a sudden they all just sit on a basketball court and go "hey I remember you! we're all friends!" "yeah we are omg!" "me too!" The scene itself was really not handled well imo, it wasn't the twist but more that it just felt totally left field for me.
And then to say that the GFs caused it, well again I don't remember any suggestions that GFs did anything bad up to that point, so when they said that it left me scratching my head and really took me out of the story.
Maybe I just paid more attention to 7 than I did 8, but Cloud's personality twist felt more natural to me and I did feel like there was plenty of suggestions earlier on, Aeris mentions Cloud looking like someone she knew very early on in the game, and there's that one forest-y town you pass through after Golden Saucer where if you go in one house you get mistaken for Zack by, correct me if I'm wrong but I beleive it was his parents (well before we know who Zack is) though I'd need to double check if it was his parents or not.
I'll give you that Tifa not speaking up about Cloud talking about things that Zack did is a bit strange, though he WAS around for all of it so she could've just thought "well Zack and Cloud were both there….I'm not sure which one did which thing but I know they were both there......"
There's also the fact that Tifa was created a bit later than the rest of the cast, basically to fill in for Aeris, so it's very possible that her connection with Cloud was shoe-horned in to make her more relevant to the overall story and they just overlooked her not putting those dots together when Cloud talked about things differently than she remembered. I also read that 7 was admittedly unpolished and unfinished, so that could very well be one of the ways it was (aside from obvious things like glitches and such)
I haven't played Crisis Core so I don't know what kind of ridiculous-ness they've added on to Sephy, Cloud, and Zack's already troubled backstory, but I never had any issue with what was told in the original game, it all seemed to jive for me every time I played.