I never said that you play Sephiroth, I heard that you fight along with Sephiroth as Zack. But anyway a friend told me that, so I guess you know better.
As for all the rest. I kind of agree with you but I also think that you have a prejudice for FF7. Yes FF7 was one of the first "3D" and it also had those FMV videos (I am not sure about the name) I also think that FF7 became so popular because it was one of the first rpgs all those people ever played. Usually the first thing you play you get attached to it. Furthermore, FF7 may not had the most interesting cast of characters but it definately had fun gameplay because of the awesome materia system and the battles, which also was so different of the repetitive class system the previous had. Anyway FF7 was great and there is no doubt about it.