There's little denying that FF7 is popular on the internet. But (and here's the real shocker) most gamers are not the ones voting in GameFAQs polls or posting on message boards. People posting on the internet and voting in polls in FF7's favor represent maybe 2% of the people who bought FF7 at most (though the ratio climbs if you go by American-only players in both categories, it's still only about 5%). The vast majority of people who have played FF7 have never given any feedback on the game outside of buying it and/or its follow-up games and movies. This highlights one of the most important pieces of decision-making in business, in fact: you cannot trust the most vocal supporters of your products to be representative of your customers as a whole.
Back on the subject of an FF7 remake, I didn't really post any definite estimates, but I wouldn't expect an FF7 remake to sell more than about 4 million worldwide lifetime (that being a best-case scenario). On top of having the disadvantage of being a remake of a successful game, it would have to contend with the series' declining popularity, and sales potential would only be further complicated by which console it was placed on.
Sky Render - Sanity is for the weak.