My favorite GBA game is The Urbz: Sims in the City. The console version of the game wasn't received very positively, but the GBA/DS version is a completely separate game, and a very good one. It's a very goofy game with a lot of stupid (read: amazing) jokes, RPG elements, mini games, some of the best music in any GBA game and a lot more. I still revisit this game once in a while.

I even played the predecessor "Sims bustin out" for the GBA a few years ago. Urbz is way more refined than bustin out, but if you liked Urbz and you want more, Bustin Out is a great way to scratch that itch.

Ambitiousamphibian did a great video on this game a few months ago. He seems to feel exactly the same about this game as I do. Because of that, I will link it, but be aware that it contains a lot of spoilers and going blind into the game is the best way to play IMO.