Interesting. FRLG are Gen 1 remakes, but are the worst selling remakes when you look at how close sales of HGSS and ORAS are to their respective games (HGSS made half the sales of GSC, ORAS did better than it even with having sales only a few million difference).
FRLG was also an attempt to get back those soured fans who couldn't transfer up to complete their Gen 3 national dex, and also fix RGBY's major issues and aesthetic. And yet it still sold pretty poorly in the long run, only barely selling more than third versions of future games (when it comes to statistics, a 2mil difference in sales in this case is not as significant as a 20mil difference in sales). Even if you exclude Yellow's sales, FRLG have a difference of roughly 21mil sales compared to their originals.
Now, comparing each set of remakes' numbers, FRLG sales are actually par for the course. But they are still the lowest-selling remakes, as HGSS and ORAS both show increases. This may indicate that remakes do indeed sell well enough compared to the first pair of games of a new gen.
Now, I do realize Gen 3's dropoff was also due to the fad dying down and people moving on. And Pokemon has experienced some nostalgia love thanks to Go's success. But just like people dropped off during Gen 3, those same people have already dropped off Go. Therefore, GF has already missed their chance to capitalize on getting back the people who grew up with the original Gen 1 games. Appealing to them now after the fact, in trying to sell a new console system and a much higher price point for the games themselves, isn't going to work.
This is why a new gen would be the smarter choice for the first Switch game.
