What about Donkey Kong: King of Swing, Pokemon Emerald, Fire Emblem 2, Donkey Kong Country 3, Yoshi Topsy Turvey, Warioware Twisted, and Mario Tennis?
It seems to me the GBA got as much meaningful first party support in 2005 as it did in 2004. We saw a huge drop off in NES support almost the minute the SNES hit (even though, as you say, there was a trickle of games coming out for years), we're just now starting to see the GBA come into a slow spot 16 months after the DS hit market... and it's not even clear at this point whether this slowdown is permanent or just Nintendo's usual quiet early spring.