Alongside what V Faction said, I'd like to point out how you cite Generation 3's lower sales in comparison to the past generations...
But how can you cite this as a fault of Generation 3? The five mainstream Pokemon games were the top five best-selling GameBoy Advance games of all time. This was a time where the popularity of portable gaming decreased as a whole, and Nintendo faced much stronger competition from Microsoft and Sony, especially the PlayStation 2, which still remains the best-selling console of all time.
Sales slumped as the franchise’s hay day died out
But how can you cite this as a fault of Generation 3? The five mainstream Pokemon games were the top five best-selling GameBoy Advance games of all time. This was a time where the popularity of portable gaming decreased as a whole, and Nintendo faced much stronger competition from Microsoft and Sony, especially the PlayStation 2, which still remains the best-selling console of all time.