Underestimate? If you weren't aware of FFVII's cultural and industrial impact, either you were living under a rock or were born with an XBOX controller in your hands.
It wasn't just FFVII, it was the platform it supported and the library it was coming into: PSX heralded the adoption of the compact disc format, and FFVII was one of the killer apps that pushed the technology and expectations for what video games could encompass. The combination of cheap, prolific media and a veritable pyroclast of anime/manga subculture in the west led to a bloom in the JRPG genre for following generations, and made FFVII a cultural monolith for the past decade and a half—just take a look at the continuing FFVII franchise games and films, something few of the following FF games have come close to replicating at even half the magnitude. It could be argued that FFVII was one game that heralded the coming of the blockbuster era of video games, with its multimedia appeal and cutting-edge graphics.
You don't even have to look at numbers or articles; just see how much FFVII
fanart continues to proliferate.
But that's just my opinion.