The GameBoy Advance may not have stuck around as long as Nintendo's other portable systems, but it still produced a pretty wonderful catalog of games.
It also produced a pretty wonderful catalog of cover art--including the five showcased in this post, which I currently consider to be my favorites.
Final Fantasy Tactics Advance--Although this game didn't click with me like its PlayStation-based predecessor, the same can't be said for its box art, which is colorful, elegant and even a bit wistful. (I'd like it to be known, by the way, that this post--and this cover art, in particular--has prompted me to give this game another shot sometime soon.)
Mr. Driller A--I'm sure some of you will question the inclusion of this piece of cover art, and I completely understand that. To be honest, I wasn't sure if I should include it myself. In the end, though, I decided it deserved a spot on the list because of its bold use of color (pink for the win!) and its adorably cheerful (and kind of retro) art style.
Ōgon no Taiyō: Ushinawareshi Toki (aka Golden Sun: The Lost Age)--True story: the box art above is my favorite of the bunch. I love that it's so stark, yet also dramatic. It certainly isn't the kind of cover art the folks at Nintendo produce every day. The question is (to those of you who've played it or its predecessor): does the game itself stack up to its beautiful box art?
Tomato Adventure--Clearly I like colorful cover art, especially when it comes to handheld games. As such, it should go without saying that I'm completely in love with Tomato Adventure's packaging, which seemingly includes every hue imaginable. Oh, and it gets bonus points for sporting an awesome logo, too.
Slime Morimori Dragon Quest--This beautiful piece of box art earned a spot in this post due in large part to the smiling slime that serves as its focus. It features plenty of other appealing elements, too, though--like Don Clawleone's shadowy presence in the background. (I'm also quite fond of this game's logo, which is a lot less busy than the ones that have been used for the Dragon Quest Monsters series.)
Honorable mentions: Final Fantasy V Advance, Guru Logi Champ, Klonoa: Empire of Dreams, Zelda no Densetsu: Fushigi no Bōshi (aka The Legend of Zelda: The Minish Cap)
See also: five favorite pieces of European DS box art, Japanese DS box art, North American DS box art, Japanese PSP box art and Japanese Wii box art