Myself, I have never played any of the prequel games of the compilation, I can't afford to be gaming in my life right now or for the past 6 years. They seem cool, I've watched clips on youtube and such.

As for Advent Children, or anything set after FFVII, they kind of don't exist in my mind. Like, it's all good. But for me, I kind of like to think after FFVII, they all lived happily ever after. Maybe because I love them so much I want that for them. They settle down; Cloud and Tifa marry, Barret becomes a responsible parent for Marlene, Vincent comes to terms with his past and maybe meets someone, etc etc etc. I like to think that's where the story ends, with the end of the original game. But that's just me!