GBA was more like an evolutionary step from the Gameboy/Gameboy Colour than a massive leap forward.
Basically was the SNES compared to the NES. It was great, but not revolutionary.
The Gameboy Advance was also only on the market for 3 years before the Nintendo DS arrived, so it never really had a chance to truly shine, but despite that, it still managed to shift 80~ million hardware units and had some extremely enjoyable games like Metroid.
The DS was a banging system, it brought something fresh and new with it's hardware... And is the number 2 best selling gaming system of all time.
--::{PC Gaming Master Race}::--