https://en.wikipedia.org/wiki/List_of_best-selling_Game_Boy_Advance_video_games
The system sold around 80 million units, much less than the following DS and a downturn from the Game Boy's collective ~120 million (though that was over the span of about 10 years and included the Gameboy Color). Still, 80 million isn't a small number, and even the 3DS which performed more poorly had more individual high-selling games, while the GBA had its Pokemon games, Mario Kart, and a few Mario ports. Everything beyond that sold less than 3 million copies. I know in general Nintendo's handhelds have often had lower attach rates since they were easy to buy for kids and more casual gamers but the GBA seems like the system that really was largely for that market. I also have to wonder if the 2D Mario ports doing so well was part of why Nintendo decided to make New Super Mario Bros on DS.
by lordlaharl422