I must be honest with you and say that I was never such a big fan of the GBA. I enjoyed the GBC a lot more actually, but that might just be because the GBC was my very first gaming system. Anyway, I don't think the software for GBA was very good, I mean, there were a few great games of course, such as MC and the Pokemon games, but that was about it. At least I think so. In that way the GBA was very similar to the GC, which also had very few good games in my opinion.
In fact, I would say that the GBA is Nintendo's worst system to date. I liked it, I just think that all other Nintendo systems are better. I have been spending a lot of time with my GBA, and I love how you can play your GBC games with it. However, to me it's the software that lowers the system, but then again, the system really was great after all.