To play GBA games, purchase a slot2 GBA expansion cart such as an EZ 3in1 or eWin 2in1. With the Bliss menu, you can run .gba files straight from your Acekard 2 once you have an EZ 3in1 or eWin 2in1 inserted in slot2. If you use the official Acekard menu, I believe you'll need a GBA loader program such as GBA ExpLoader, available in the download section.
And as Destructobot pointed out, using the Bliss menu lets you use the CHEAT.DAT database without having to rebuild your cheats for each game every time you update it.
-Bri