This really was a brilliant system and you've highlighted a few of its best. Golden Sun was such a rich and enjoyable RPG when it came out - I have fond memories of sinking so many hours into it.
I've still got a GBA SP with a bunch of cartridges, and have a GBA emulator on my PSP. Fire Emblem and Advance Wars were another two that really grabbed me, as well as the GBA's version of Street Fighter Alpha 3. Crawfish did such a spectacular job cramming so much game onto that tiny little handheld.
Nice little nostalgia piece here - thanks @ushinaitakunai :)