I can tell you why I instantly fell in 'love' with FF7.
1. FF7, was THE best graphical game I had ever saw, when it came out. (mind you I didn't have anything that resembled a PC back then, I still had a comadore 64!)
2. FF7's cast was by far the most complex cast I had ever seen. They actually had a 'story' to them, and unlike FF6's 'shallow back story' in that, they had one, it was just very non-central to the story, or you didn't find out much about a persons backstory as it wasn't directly 'told' (Aka shadow & his possible daughter).
3. Aerith. Everyones loved Aerith, and every time I played that game, and Sepiroth killed Aerith, I shed a tear. It is the ONLY game that has ever gone so far as to make Me actually get attached to a character, and then have the main villian kill her and leaving you powerless to stop it. Sepiroth was the Villian you WANTED to get vengence for killing Aerith.
I have never played a game aside from FF7 that has actually made me get attached to a character, let alone make me Want to kill the badguy on an 'emotional level'.
Now, that doesnt mean that I think FF7 is the greatest game of all fucking time.
No, That is a tie beween Chrono Trigger, and FF6.
Kefka alone makes FF6 > FF7.