FF7 was so popular because it introduced the Final Fantasy franchise to a whole new group of players, it got players like myself who had never played a RPG before sucked right in. It had great characters, story, graphics/cenematics and gameplay for its time.
For ME, it made me backtrack and try out FF3 and Crono Trigger/Cross.
FF8 and 10 were also good, if not better obviously.. but FF7 resparked the Final Fantasy name in North America. I thought FF9 was an OK game, and the cenematics were top notch.. but I didn't see the point in changing the graphical style when 7 and 8 were what everyone wanted.
One of the biggest complaints I ever heard about FF7 was the ol' block hands lol.
What did everyone think of FF12? I thought it was a good change of combat style, gave it the old MMO edge too it. But the 'skill tree' could have used a little more ablilities.