I never really understood the hate that has rose against 7, I will say that I didn't enjoy it that much and I don't really know why. In my personal experience most of my friends really like the game and the reason they give is because of nostalgia, they played it when it was released, we were 7-8, but I didn't.
I played it for the first time last year with a friend and they were reminiscing telling me stories of this boss and that plot point, and I just couldn't get into it. For me X was my favourite, maybe because it was newer, I do find that age of graphics unappealing, which is weird because I play mostly retro games these days. I know why I like X so much and I know that it was not the game, but for a disgustingly subjective reason so doesn't have any place in an actual debate. I didn't particularly like any past X because I hate the real time battle systems, for me, they have lost all strategy that the earlier games had, where for some fights you had to sit and figure out how to win, with 13 in particular I didn't even know what I was doing, I just spammed 'X' and beat the game.
OT: For those of my friends who like it, it is nostalgia and they admit that. Maybe the hate comes from over zealous people who don't understand why so many like it. Conversely maybe the 'fanboys' who so adamantly bestow and defend its God like status and agitate so many, realised that it wasn't as good as they remember and get tetchy about it, one of my friends in particular is like this. When drunk, she admits she has actually had a growing hatred for it on her recent play through. For me, if you enjoy a game good, if you don't, you don't. There is no need to attack others for a different opinion. Most forget the difference between opinion and fact.