It's an interesting fact, that the GBA is actually a 32 bit device, it's just not equipped with 3D processing capabilities.
According to Wikipedia it's what Nintendo had envisioned for the successor to the Gameboy, but could'nt pull it off at the time, (for a myriad of reasons) so they went with the GBC instead.
It can however handle 16 bit and lower system emulation, wich would explain how it can handle TurboGrafx-16 emulation and the SNES to GBA game conversions (via flashcard (at least on Supercard-SD)), like how we saw alot of GBA versions of SNES games, such as Final Fantasy IV, V, VI, Doom 1 and 2, the Legend of Zelda: a Link to the Past, Rock and Roll Racing, Blackthorne, etc, etc...