I HOPE this has been said already, but in case it hasn't.. The tie ratio for GBA sucks because you only need 1 or a couple games. When you are at home why play a shitty GBA? Play on a big tv with great graphics, multiplayer, online. People typically only play portables on the road, and if you are on the road, odds are there is a reason you are on the road. So you only play it when you are away from home AND not doing something.
So people play when they aren't driving, when they are being dragged around a shopping center, waiting for an appointment, etc. And a 10+ hour game is going to stretch for months if that is the only time you play it.
I remember I got a GBA and bought like 8 games, ended up playing half of them to completion (AWars, Metroids, Castlevanias). I haven't had an opportunity to play a GBA in over a year, except at home. And I'd rather play xbox or GC at home. I've thought about buying a GBplayer for GC to finish up golden sun, pokemon, etc, but why bother.