The biggest series when it comes to Japanese role-playing games is Final Fantasy. At least in the West. In Japan it's not as obvious and here the Dragon Quest series has usually attracted the most attention and has actually sold far more.
Today we get a nice confirmation of how popular the series actually is via Famitsu, which reveals that Dragon Quest III HD-2D Remake sold an astounding 826,945 copies (of which 641,195 for Switch) during its first week on the market. That's over ten times the rest of the top 10 combined, and perhaps more impressively... it means, according to Genki, that the game will "instantly become the number 1 best-selling game in Japan for the whole of 2024".
It's also worth mentioning that according to Genki, the game is sold out in many places, so if there had just been more available in stores, sales would have been even higher...
Thanks, VGC.