Baldur's Gate: Dark Alliance for the GBA is a competent action RPG, and a decent interpretation of the console version.
Gameplay remains the same, which players of this genre are familiar with. You pick from one of three characters: a fighter, a wizard, and an archer, and advance through sewers, forests, castles, and other environments, fighting enemies and leveling up, collecting gold, and raiding chests for items and weapons. As you level up, you gain points to upgrade different skills.
The developers had to work with the technical limitations of the GBA, and these are sometimes painfully apparent. At times, there's a lot going on, and when there are many onscreen enemies and fireballs flying, you'll experience slowdown. Sounds are sparse, and the yelps and screams of enemies are repeated. There's no music in the game except at certain points that signal an important section of the game is coming up. In fact, for most of the game all you'll hear are your footsteps.
It's understandable that concessions had to be made for a GBA version of the game, but if you've played the console version, there are still omissions and differences that stand out. The most obvious is the absence of the automap, which was extremely useful. There's no replacement for this at all, not even a flat 2D map that you can bring up.
Although the GBA version has save points at checkpoints during your journey which look just like they do on the console version, there's only one save slot. However, the game allows you to save anywhere, with a caveat. If you don't save at a save point, only your stats are saved, not your location.
While there are red healing and blue rejuvenation potions like in the console version, the recall potions are curiously missing, which is annoying for players who want to sell their loot for gold, since your character has a limited carrying capacity, and this ends up in a lot of backtracking to merchants. Since enemies respawn when you exit and enter an area, getting back to where you were means you'll have to fight through them again.
Your character can't jump, which is not something you won't miss, as it was goofy anyway, and didn't have many useful applications.
You pretty much know what you're getting with a game in this genre, and unfortunately there's nothing really exceptional about Baldur's Gate: Dark Alliance for the GBA. It is a competent action RPG, and a decent interpretation of the console version.