You're very welcome to prove me wrong. But even so, the point is that videogame remakes almost never outsell their original counterparts, no matter how well made or high profile they are.
Proving the thesis "The remake of Final Fantasy VII will not outsell the original release" using the argument that almost never a remake outsold the original game is not very convincing.
First, how much did the original game sell? Only on PS1 or counting PC sales too? What about re-releases?
Second, each remake is a league of its own. Sales depend on so many factors: how long the time span between the two releases is, how much "new" the remake feels/is perceived, whether the franchise is still popular or not, whether the IP has been cultivated or not during the years, which business model is adopted to sell the remake.
We have plenty of recent examples of remakes selling almost as well as original releases. Think about the Crash trilogy, which sold 10m and counting (more than each entry though lower than all entries combined). Or about Pokémon OmegaRuby/AlphaSApphire, which sold 14.23m against 16.22 of the original release. Link's Awakening too will outsell the original game.
If Final Fantasy VII won't outsell the original game it's because it'll have a worse reception. But with a big launch which is guaranteed, how Square has cultivated the FFVII sub-franchise over time, its technical achievement, and re-releases that will definitely happen on PS5 and PC expecting less than 10m is a bit weird imo.