The first of the original Duology, Golden Sun pushes the GBA to its limits. Everything in the game moves very fluidly, and Motoi Sakuraba makes the GBA create sounds I didn't even know were possible with his progressive rock-inspired soundtrack. The Djinn class system can feel a bit overwhelming at first, but once you get a handle on it it is easily one of my favorite overall combat systems in a turn-based RPG.
The primary thing that holds Golden Sun back is its writing. The plot overall is alright (and keep in mind this is only half of it), but the dialogue is very long-winded, often repeats itself, and just generally slows the game to a crawl. I have a relatively high tolerance for this type of thing--especially since it is not voice acted--but if constant, drawn-out cutscenes are a dealbreaker for you, you may want to look elsewhere.
The primary thing that holds Golden Sun back is its writing. The plot overall is alright (and keep in mind this is only half of it), but the dialogue is very long-winded, often repeats itself, and just generally slows the game to a crawl. I have a relatively high tolerance for this type of thing--especially since it is not voice acted--but if constant, drawn-out cutscenes are a dealbreaker for you, you may want to look elsewhere.