Hoo boy, the GBA is so great! The Castlevania games are my favorites, though I think Circle of the Moon is the weakest of the bunch by quite a bit. But let me mention a couple games not on your list.
I believe I've sung the praises of Astro Boy: Omega Factor before. Crafted by the mad geniuses at Treasure, it is a superb action game. Gunstar Super Heroes, the sequel to their classic Genesis game, is also quite good.
Drill Dozer is a great action platformer by Game Freak. Great music, fun gameplay, and the cartridge had a built-in rumble feature.
Mario vs. Donkey Kong is unlike the Lemmings-esque series that followed it but is rather a true sequel to Donkey Kong '94. It doesn't quite reach those heights but it's a good time all the same.



