The shortness of the GBA's life tends to be increasingly exaggerated. It had a fine year of releases in 2005. It was certainly being shooed out the door past that, but something as notable as FFVI Advance saw western release in 2007.
As far as the GBA vs. DS debate goes, I'm team GBA all the way:
2 great 2D Metroids >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Hunters & Pinball
Minish Cap & LTTP >>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Phantom Hourglass & Spirit Tracks
Warioland 4, WarioWare & Twisted >>>>>>>>>>>>>>>>>>>>>>>>>>> Master of Disguise, Touched, & DIY
FE6, 7, & Sacred Stones >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Shadow Dragon & Heroes of Light & Shadow
Advance Wars 1&2 >>>>>>>>>>> Dual Strike & Days of Ruin
Ports of the best Mario games w/ additional content >>>>>>>>>>>>>>>>>>>>>>>>>>>>> bland-ass NSMB
Mario Golf & Tennis >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>No Mario Golf or Tennis
Mario vs. DK 1 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>any other Mario vs. DK that came afterward
Mario & Luigi Superstar Saga >>> any other M&L game (Bowser's Inside Story is close, tho)
Golden Sun & TLA >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Dark Moon
Rhythm Tengoku >>> Rhythm Heaven Gold
Megaman Zero & Battle Network series >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> ZX & StarForce
Aria of Sorrow >>>>>>>>> any DS Castlevania